# kb

id: mannheim-process-20260505-0
file: data/en.wikipedia.org/wiki/Mannheim_process-0.md
category: reference
title: Mannheim process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mannheim_process
date_saved: 2026-05-05T10:48:58.970059+00:00
instance: kb-cron
parent: mannheim-process-20260505-0
summary:
The Mannheim process is an industrial process for the production of hydrogen chloride and sodium sulfate from sulfuric acid and sodium chloride. The Mannheim furnace is also used to produce potassium sulfate from potassium chloride. The Mannheim process is a stage in the Leblanc process for the production of sodium carbonate. == Process == The process is named after Mannheim furnace, a large cast iron kiln in which it is conducted. The furnace was developed at Verein Chemischer Fabriken in Mannheim at the turn of the 20th century and superseded earlier furnace designs formerly used for the same purpose. Sodium chloride and sulfuric acid are first fed onto a stationary reaction plate where an initial reaction takes place. The stationary plate is up to 6 m (20 ft) in diameter. Rotating rabble arms constantly turn over the mixture and move the intermediate product to a lower plate. The kiln portion of the furnace is constructed with bricks that have high resistance to direct flame, temperature, and acid. The other parts of the furnace are heat and acid resistant. Hot flue gas passes up over the plates carrying out liberated hydrogen chloride gas. The intermediate product reacts with more sodium chloride


id: mass-deacidification-20260505-0
file: data/en.wikipedia.org/wiki/Mass_deacidification-0.md
category: reference
title: Mass deacidification
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_deacidification
date_saved: 2026-05-05T10:49:00.170656+00:00
instance: kb-cron
parent: mass-deacidification-20260505-0
summary:
Mass deacidification is a term used in library and information science as one possible measure against the degradation of paper in old books, the so-called "slow fires". The goal of the process is to increase the pH of acidic paper. Although acid-free paper has become more common, a large body of acidic paper still exists in books made after the 1850s; this is because of its cheaper and simpler production methods. Acidic paper, especially when exposed to light, air pollution, or high relative humidity, yellows and becomes brittle over time. During mass deacidification an alkaline agent is deposited in the paper to neutralize existing acid and prevent further decay. Mass deacidification is intended for objects on acidic paper that will be lost if no action is performed. == History of research and process development == Mass deacidification—along with microfilm and lamination—was developed during the early and mid-20th century as a response to the chemical process of hydrolysis by which the fibers that constitute paper, providing its structure and strength, have their bonds broken, resulting in paper that becomes increasingly brittle over time. Environmental pollutants can react with paper to form acids that promote oxidation, creating more acid as a by-product,


id: mass-deacidification-20260505-1
file: data/en.wikipedia.org/wiki/Mass_deacidification-1.md
category: reference
title: Mass deacidification
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_deacidification
date_saved: 2026-05-05T10:49:00.170656+00:00
instance: kb-cron
parent: mass-deacidification-20260505-0
summary:
The BookKeeper process is a non-aqueous, liquid phase process that uses magnesium oxide. BookKeeper is available through Preservation Technologies, L.P. with plants in the U.S., Spain, Japan, Poland, The Netherlands, South Africa, Qatar. Another plant is available through Fratielivi in Italy. The CSC Book Saver uses carbonated magnesium propylate for deacidification. The CSC Book Saver is available in Europe through Conservación de Sustratos Celulósicos S.L. (CSC) (Barcelona, Spain). The Papersave process was developed by Battelle Ingenieurtechnik GmbH and is, therefore, sometimes referred to as "the Battelle Process". The process uses magnesium titanium alkoxide. The Papersave process is available in Europe through Nitrochemie Wimmis (Wimmis, Switzerland) under the name of Papersave Swiss and the Zentrum für Bucherhaltung (Leipzig, Germany). The Wei T'o process uses methoxy magnesium methyl carbonate, or isopropoxy magnesium isopropyl carbonate, and new products are coming out in 2008. Wei T'o is less commonly used for mass deacidification treatment than for single item deacidification. Wei T'o products are available through Wei T'o Associates Inc. (Matteson, US). BookKeeper, CSC Booksaver, Papersave, and Wei T'o are also available as hand-held sprays. == Adoption and costs == While deacidification has been adopted by major research libraries such as the Library of Congress


id: mercury-silvering-20260505-0
file: data/en.wikipedia.org/wiki/Mercury_silvering-0.md
category: reference
title: Mercury silvering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mercury_silvering
date_saved: 2026-05-05T10:49:01.355366+00:00
instance: kb-cron
parent: mercury-silvering-20260505-0
summary:
Mercury silvering or fire gilding is a silvering technique for applying a thin layer of precious metal such as silver or gold (mercury gilding) to a base metal object. The process was invented during the renaissance and is documented in Vannoccio Biringuccio's 1540 book De la pirotechnia. An amalgam of mercury and the precious metal is prepared and applied to the object which is then heated, sometimes in oil, vaporizing most of the mercury. The technique is dangerous since mercury is highly toxic, especially in its vapor phase. Mercury silvering can be detected through a variety of methods. The technique was also used in Asia, for example tokin plating in Edo-period Japan. == See also == Mercury glass, internally silvered decorative glass products named for their resemblance to mercury Liquid-mirror telescope, may use a layer of reflective mercury == References ==


id: merox-20260505-0
file: data/en.wikipedia.org/wiki/Merox-0.md
category: reference
title: Merox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Merox
date_saved: 2026-05-05T10:49:02.530750+00:00
instance: kb-cron
parent: merox-20260505-0
summary:
Merox is an acronym for mercaptan oxidation. It is a proprietary catalytic chemical process developed by UOP used in oil refineries and natural gas processing plants to remove mercaptans from LPG, propane, butanes, light naphthas, kerosene, and jet fuel by converting them to liquid hydrocarbon disulfides. The Merox process requires an alkaline environment which, in some process versions, is provided by an aqueous solution of sodium hydroxide (NaOH), a strong base, commonly referred to as caustic. In other versions of the process, the alkalinity is provided by ammonia, which is a weak base. The catalyst in some versions of the process is a water-soluble liquid. In other versions, the catalyst is impregnated into charcoal granules. Processes within oil refineries or natural gas processing plants that remove mercaptans and/or hydrogen sulfide (H2S) are commonly referred to as sweetening processes because they result in products which no longer have the sour, foul odors of mercaptans and hydrogen sulfide. The liquid hydrocarbon disulfides may remain in the sweetened products. These may be used as part of the refinery or natural gas processing plant fuel, or they may be processed further. When dealing with kerosene, the Merox process is usually more economical than using


id: merox-20260505-1
file: data/en.wikipedia.org/wiki/Merox-1.md
category: reference
title: Merox
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Merox
date_saved: 2026-05-05T10:49:02.530750+00:00
instance: kb-cron
parent: merox-20260505-0
summary:
=== Flow diagram === The flow diagram below depicts the equipment and the flow paths involved in the process. The LPG (or light naphtha) feedstock enters the prewash vessel and flows upward through a batch of caustic which removes any H2S that may be present in the feedstock. The coalescer at the top of the prewash vessel prevents caustic from being entrained and carried out of the vessel. The feedstock then enters the mercaptan extractor and flows upward through the contact trays where the LPG intimately contacts the downflowing Merox caustic that extracts the mercaptans from the LPG. The sweetened LPG exits the tower and flows through: a caustic settler vessel to remove any entrained caustic, a water wash vessel to further remove any residual entrained caustic and a vessel containing a bed of rock salt to remove any entrained water. The dry sweetened LPG exits the Merox unit. The caustic solution leaving the bottom of the mercaptan extractor ("rich" Merox caustic) flows through a control valve which maintains the extractor pressure needed to keep the LPG liquified. It is then injected with UOP's proprietary liquid catalyst (on an as needed basis), flows through a steam-heated heat exchanger and is


id: metal-vapor-synthesis-20260505-0
file: data/en.wikipedia.org/wiki/Metal_vapor_synthesis-0.md
category: reference
title: Metal vapor synthesis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Metal_vapor_synthesis
date_saved: 2026-05-05T10:49:03.899826+00:00
instance: kb-cron
parent: metal-vapor-synthesis-20260505-0
summary:
In chemistry, metal vapor synthesis (MVS) is a method for preparing metal complexes by combining freshly produced metal atoms or small particles with ligands. In contrast to the high reactivity of such freshly produced metal atoms, bulk metals typically are unreactive toward neutral ligands. The method has been used to prepare compounds that cannot be prepared by traditional synthetic methods, e.g. Ti(η6-toluene)2. The technique relies on a reactor that evaporates the metal, allowing the vapor to impinge on a cold reactor wall that is coated with the organic ligand. The metal evaporates upon being heated resistively or irradiated with an electron beam. The apparatus operates under high vacuum. In a common implementation, the metal vapor and the organic ligand are co-condensed at liquid nitrogen temperatures. In several case where compounds are prepared by MVS, related preparations employ conventional routes. Thus, tris(butadiene)molybdenum was first prepared by co-condensation of butadiene and Mo vapor, but yields are higher for the reduction of molybdenum(V) chloride in the presence of the diene. == References ==


id: metal-induced-crystallization-20260505-0
file: data/en.wikipedia.org/wiki/Metal-induced_crystallization-0.md
category: reference
title: Metal-induced crystallization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Metal-induced_crystallization
date_saved: 2026-05-05T10:49:05.059664+00:00
instance: kb-cron
parent: metal-induced-crystallization-20260505-0
summary:
Combined with certain metallic species, amorphous films can crystallize in a process known as metal-induced crystallization (MIC). The effect was discovered in 1969, when amorphous germanium (a-Ge) films crystallized at surprisingly low temperatures when in contact with aluminum, silver, copper, or tin. The effect was also verified in amorphous silicon (a-Si) films, as well as in amorphous carbon and various metal-oxide films. Likewise, the MIC evolved from simple temperature-driven annealing approaches to others involving lasers or microwave radiation, for example. A very common variant of the MIC procedure is the metal-induced lateral crystallization (MILC). In this case, the metal is deposited (onto the top or at the bottom) of some selected areas of the desired amorphous film. Upon annealing, crystallization starts from the portion of the amorphous film that is in contact with the metal species, and the MIC proceeds laterally. == References ==


id: methanation-20260505-0
file: data/en.wikipedia.org/wiki/Methanation-0.md
category: reference
title: Methanation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methanation
date_saved: 2026-05-05T10:49:06.202076+00:00
instance: kb-cron
parent: methanation-20260505-0
summary:
Methanation is the conversion of carbon monoxide and carbon dioxide (COx) to methane (CH4) through hydrogenation. The methanation reactions of COx were first discovered by Sabatier and Senderens in 1902. COx methanation has many practical applications. It is a means of carbon oxide removal from process gases and is also being discussed as an alternative to PROX in fuel processors for mobile fuel cell applications. Methanation as a means of producing synthetic natural gas has been considered since the 1970s. More recently it has been considered as a way to store energy produced from solar or wind power using power-to-gas systems in conjunction with existing natural gas storage. == Chemical reactions == The following reactions describe the methanation of carbon monoxide and carbon dioxide respectively: CO + 3 H 2 ⟶ CH 4 + H 2 O {\displaystyle {\ce {CO + 3H2 -> CH4 + H2O}}} △H = -206 kJ/mol CO 2 + 4 H 2 ⟶ CH 4 + 2 H 2 O {\displaystyle {\ce {CO2 + 4H2 -> CH4 + 2 H2O}}} △H = -164 kJ/mol The methanation reactions are highly exothermic and release significant amounts of heat during reaction completion. There is disagreement on whether the CO2


id: micro-compounding-20260505-0
file: data/en.wikipedia.org/wiki/Micro-compounding-0.md
category: reference
title: Micro-compounding
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Micro-compounding
date_saved: 2026-05-05T10:49:07.395983+00:00
instance: kb-cron
parent: micro-compounding-20260505-0
summary:
Micro-compounding is the mixing or processing of polymer formulations in the melt on a small scale, typically milliliters. It is popular for research and development because it gives faster, more reliable results with smaller samples and less cost. Its applications include pharmaceutical, biomedical, and nutritional areas. == Design == Micro-compounding is typically performed with a tabletop, twin screw micro-compounder, or micro-extruder with a working volume of 5 or 15 milliliters. With such small volumes, it is difficult to have sufficient mixing in a continuous extruder. Therefore, micro-compounders typically have a batch mode (recirculation) and a conical shape. The L/D of a continuous twin screw extruder is mimicked in a batch micro-compounder by the recirculation mixing time, which is controlled by a manual valve. With this valve, the recirculation can be interrupted to unload the formulation in either a strand or an injection moulder, a film device or a fiber line. Typical recirculation times are one to three minutes, depending on the ease of dispersive and distributive mixing of the formulation. == Benefits == Micro-compounding can now produce films, fibers, and test samples (rods, rings, tablets) from mixtures as small as 5 ml in less than ten minutes. The small footprint


id: micro-pulling-down-20260505-0
file: data/en.wikipedia.org/wiki/Micro-pulling-down-0.md
category: reference
title: Micro-pulling-down
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Micro-pulling-down
date_saved: 2026-05-05T10:49:08.623875+00:00
instance: kb-cron
parent: micro-pulling-down-20260505-0
summary:
The micro-pulling-down (μ-PD) method is a crystal growth technique based on continuous transport of the melted substance through micro-channel(s) made in a crucible bottom. Continuous solidification of the melt is progressed on a liquid/solid interface positioned under the crucible. In a steady state, both the melt and the crystal are pulled-down with a constant (but generally different) velocity. Many different types of crystal are grown by this technique, including Y3Al5O12, Si, Si-Ge, LiNbO3, α-Al2O3, Y2O3, Sc2O3, LiF, CaF2, BaF2, etc. == Crystal growth routine == Standard routine procedure used in the growth of most of μ-PD crystals is well developed. The general stages of the growths include: Charging of the crucible with starting materials (mixture of powders) Heating of the crucible until starting materials in the crucible are completely melted Upward displacement of the seed until its contact with the meniscus or crucible Formation of the meniscus and partial melting of the seed top Correction of the shape of the meniscus through appropriate adjustment of crucible temperature and position of the seed crystal Crystal growth through pulling of the seed in downward direction Separation of the as grown crystal from the meniscus Cooling of the system (including the crystal and


id: molecular-laser-isotope-separation-20260505-0
file: data/en.wikipedia.org/wiki/Molecular_laser_isotope_separation-0.md
category: reference
title: Molecular laser isotope separation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_laser_isotope_separation
date_saved: 2026-05-05T10:49:09.777690+00:00
instance: kb-cron
parent: molecular-laser-isotope-separation-20260505-0
summary:
Molecular laser isotope separation (MLIS) is a method of isotope separation, where specially tuned lasers are used to separate isotopes of uranium using selective ionization of hyperfine transitions of uranium hexafluoride molecules. It is similar to AVLIS. Its main advantage over AVLIS is low energy consumption and use of uranium hexafluoride instead of vaporized uranium. MLIS was conceived in 1971 at the Los Alamos National Laboratory. MLIS operates in cascade setup, like the gaseous diffusion process. Instead of vaporized uranium as in AVLIS the working medium of the MLIS is uranium hexafluoride which requires a much lower temperature to vaporize. The UF6 gas is mixed with a suitable carrier gas (a noble gas including some hydrogen) which allows the molecules to remain in the gaseous phase after being cooled by expansion through a supersonic de Laval nozzle. A scavenger gas (e.g. methane) is also included in the mixture to bind with the fluorine atoms after they are dissociated from the UF6 and inhibit their recombination with the enriched UF5 product. In the first stage, the expanded and cooled stream of UF6 is irradiated with an infrared laser operating at the wavelength of 16 μm. The mix is then irradiated with


id: molecular-layer-deposition-20260505-0
file: data/en.wikipedia.org/wiki/Molecular_layer_deposition-0.md
category: reference
title: Molecular layer deposition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_layer_deposition
date_saved: 2026-05-05T10:49:10.956175+00:00
instance: kb-cron
parent: molecular-layer-deposition-20260505-0
summary:
Molecular layer deposition (MLD) is a vapour phase thin film deposition technique based on self-limiting surface reactions carried out in a sequential manner. Essentially, MLD resembles the well established technique of atomic layer deposition (ALD) but, whereas ALD is limited to exclusively inorganic coatings, the precursor chemistry in MLD can use small, bifunctional organic molecules as well. This enables, as well as the growth of organic layers in a process similar to polymerization, the linking of both types of building blocks together in a controlled way to build up organic-inorganic hybrid materials. Even though MLD is a known technique in the thin film deposition sector, due to its relative youth it is not as explored as its inorganic counterpart, ALD, and a wide sector development is expected in the upcoming years. == History == Molecular layer deposition is a sister technique of atomic layer deposition. While the history of atomic layer deposition dates back to the 1970s, thanks to the independent work of Valentin Borisovich Aleskovskii. and Tuomo Suntola, the first MLD experiments with organic molecules were not published until 1991, when an article from Tetsuzo Yoshimura and co-workers appeared regarding the synthesis of polyimides using amines and anhydrides as


id: molecular-layer-deposition-20260505-1
file: data/en.wikipedia.org/wiki/Molecular_layer_deposition-1.md
category: reference
title: Molecular layer deposition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_layer_deposition
date_saved: 2026-05-05T10:49:10.956175+00:00
instance: kb-cron
parent: molecular-layer-deposition-20260505-0
summary:
== Process chemistry and surface reactions == Precursor chemistry plays a key role in MLD. The chemical properties of the precursor molecules drive the composition, structure and stability of the deposited hybrid material. To reach the saturation stage in a short time and ensure a reasonable deposition rate, precursors must chemisorb on the surface, react rapidly with the surface active groups and react with each other. The desired MLD reactions should have a large negative ∆G value. Organic compounds are employed as precursors for MLD. For their effective use, the precursor should have sufficient vapor pressure and thermal stability to be transported in the gas phase to the reaction zone without decomposing. Volatility is influenced by the molecular weight and intermolecular interactions. One of the challenges in MLD is to find an organic precursor that has sufficient vapor pressure, reactivity and thermal stability. Most organic precursors have low volatility, and heating is necessary to ensure the sufficient supply of vapor reaching the substrate. The backbone of the organic precursors can be flexible i.e., aliphatic, or rigid i.e., aromatics employed with the functional groups. The organic precursors usually are homo or heterobifunctional molecules with -OH, -COOH, -NH2, -CONH2, -CHO, -COCl, -SH,


id: molecular-layer-deposition-20260505-2
file: data/en.wikipedia.org/wiki/Molecular_layer_deposition-2.md
category: reference
title: Molecular layer deposition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_layer_deposition
date_saved: 2026-05-05T10:49:10.956175+00:00
instance: kb-cron
parent: molecular-layer-deposition-20260505-0
summary:
Molecule tilting: organic molecules with long chains are prone to not remaining completely perpendicular to the surface, lowering the number of surface sites. Bidentate ligands: when a reacting molecule has two functional groups, it may bend and react with two surface sites instead of remaining straight on the surface. This has been shown, for instance, for titanicones grown with ethylene glycol and glycerol. Because glycerol has an additional hydroxyl group compared to ethylene glycol and is able to provide an extra reactive hydroxyl group in the case of a double reaction of the terminal hydroxyl groups with the surface. Steric hindrance: organic precursors are often bulky, and can cover several surface groups when attached to the surface. Long pulsing times: organic precursors can have very low vapour pressures, and very long pulsing times may be necessary in order to achieve saturation. In addition, long purging times are usually needed to remove all unreacted molecules from the chamber afterward. Low temperatures: to increase the precursor vapor pressure, one might think of increasing its temperature. Nevertheless, organic precursors are usually very thermally fragile, and a temperature increase may induce decomposition. Gas-phase: many organic reactions are normally carried out in the liquid phase,


id: molecular-layer-deposition-20260505-3
file: data/en.wikipedia.org/wiki/Molecular_layer_deposition-3.md
category: reference
title: Molecular layer deposition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_layer_deposition
date_saved: 2026-05-05T10:49:10.956175+00:00
instance: kb-cron
parent: molecular-layer-deposition-20260505-0
summary:
==== Gaseous precursors ==== ALD/MLD are both gas phase processes. Hence, precursors are required to be introduced into the reaction zones in their gaseous form. A precursor already existing in a gaseous physical state would make its transport to the reactor very straightforward and hassle free. For example, there will be no need of heating the precursor thereby reducing the risk of condensation. However, precursors are seldom available in gaseous state. On the other hand, some ALD co-reactants are available in gaseous form. Examples include H2S used for sulphide films; NH3 used for nitride films; plasmas of O2 and O3 to produce oxides. The most common and straight forward way of regulating the supply of these co-reactants to the reactor is using a mass flow controller attached between the source and the reactor. They can also be diluted with an inert gas to control their partial pressure. == Film characterisation == Several characterisation techniques have evolved over time as the demand for creating ALD/MLD films for different applications has increased. This includes lab-based characterisation and efficient synchrotron-based x-ray techniques. === Lab-based characterisation === Since they both follow a similar protocol, almost all characterisation applicable to ALD generally applies to MLD


id: molecular-layer-deposition-20260505-4
file: data/en.wikipedia.org/wiki/Molecular_layer_deposition-4.md
category: reference
title: Molecular layer deposition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_layer_deposition
date_saved: 2026-05-05T10:49:10.956175+00:00
instance: kb-cron
parent: molecular-layer-deposition-20260505-0
summary:
==== High-k ==== Novel organic thin-film transistors require a high-performance dielectric layer, which should be thin and possess a high k-value. MLD makes tuning the high-k and dielectric strength possible by altering the amount and the ratio of the organic and inorganic components. Moreover, the usage of MLD allows to achieve better mechanical properties in terms of flexibility. Various hybrid dielectrics have already been developed: zincone hybrids from zirconium tert-butoxide (ZTB) and ethylene glycol (EG); Al2O3 based hybrids such as self-assembled MLD-deposited octenyltrichlorosilane (OTS) layers and Al2O3 linkers. Additionally, dielectric Ti-based hybrid from TiCl4 and fumaric acid proved its applicability in charge memory capacitors. === MLD for porous materials === MLD has high potential for the deposition of porous hybrid organic-inorganic and purely organic films, such as Metal-Organic Frameworks (MOFs) and Covalent-Organic Frameworks (COFs). Thanks to the defined pore structure and chemical tunability, thin films of these novel materials are expected to be incorporated in the next generation of gas sensors and low-k dielectrics. Conventionally, thin films of MOFs and COFs are grown via solvent-based routes, which are detrimental in a cleanroom environment and can cause corrosion of the pre-existing circuitry. As a cleanroom-compatible technique, MLD presents an attractive alternative,


id: molecular-layer-deposition-20260505-5
file: data/en.wikipedia.org/wiki/Molecular_layer_deposition-5.md
category: reference
title: Molecular layer deposition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_layer_deposition
date_saved: 2026-05-05T10:49:10.956175+00:00
instance: kb-cron
parent: molecular-layer-deposition-20260505-0
summary:
==== Bioactive and biocompatible surfaces ==== MLD can also be applied to design of bioactive and biocompatible surfaces for targeted cell and tissue responses. Bioactive materials involve materials for regenerative medicine, tissue engineering (tissue scaffolds), biosensors etc. The important factors that can affect the cell-surface interaction, as well as the immune response of the system are surface chemistry (e.g. functional groups, surface charge and wettability) and surface topography. Understanding these properties is crucial in order to control the attachment and proliferation of the cell, and resultant bioactivity of the surfaces. Furthermore, the choice of organic building blocks and a type of biomolecules (e.g. proteins, peptides or polysaccharides) during the formation of bioactive surfaces is a key factor for cellular response of the surface. MLD allows for the building of bioactive, precise structures by combining such organic molecules with inorganic biocompatible elements like titanium. The use of MLD for biomedical applications is not widely studied and is a promising field of research. This method enables surface modification and thus, can functionalize a surface. A recent study published in 2017 used MLD to create bioactive scaffolds by combining titanium clusters with amino acids such as glycine, L-aspartic acid and L-arginine as organic


id: mond-process-20260505-0
file: data/en.wikipedia.org/wiki/Mond_process-0.md
category: reference
title: Mond process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mond_process
date_saved: 2026-05-05T10:49:12.151423+00:00
instance: kb-cron
parent: mond-process-20260505-0
summary:
The Mond process, sometimes known as the carbonyl process, is a technique created by Ludwig Mond in 1890, to extract and purify nickel. The process was used commercially before the end of the 19th century, and particularly by the International Nickel Company in the Sudbury Basin. This process converts nickel oxides into nickel metal with very high purity being attainable in just a single step. == Synopsis == This process involves the fact that carbon monoxide combines with nickel readily and reversibly to give nickel carbonyl. Few other elements other than nickel, iron, and cobalt form carbonyl compounds under the mild conditions used in the process. This process has three steps: 1. Metal Feed (consisting of primarily Nickel oxide) reacts with hydrogen at 200 °C to give nickel. Other impurities including iron and cobalt are also reduced. NiO(s) + H2(g) → Ni(s) + H2O(g) 2. The impure nickel reacts with carbon monoxide at 50–60 °C to form the gas nickel carbonyl, leaving the impurities as solids. Ni(s) + 4 CO(g) → Ni(CO)4(g) 3. The mixture of nickel carbonyl and carbon monoxide is heated to 220–250 °C, resulting in decomposition back to nickel and carbon monoxide: Ni(CO)4(g) → Ni(s) + 4


id: monsanto-process-20260505-0
file: data/en.wikipedia.org/wiki/Monsanto_process-0.md
category: reference
title: Monsanto process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Monsanto_process
date_saved: 2026-05-05T10:49:13.296370+00:00
instance: kb-cron
parent: monsanto-process-20260505-0
summary:
The Monsanto process is an industrial method for the manufacture of acetic acid by catalytic carbonylation of methanol. The Monsanto process has largely been supplanted by the Cativa process, a similar iridium-based process developed by BP Chemicals Ltd, which is more economical and environmentally friendly. This process operates at a pressure of 30–60 atm and a temperature of 150–200 °C and gives a selectivity greater than 99%. It was developed in 1960 by the German chemical company BASF and improved by the Monsanto Company in 1966, which introduced a new catalyst system. == Catalytic cycle == The catalytically active species is the anion cis-[Rh(CO)2I2]− (top of scheme). The first organometallic step is the oxidative addition of methyl iodide to cis-[Rh(CO)2I2]− to form the hexacoordinate species [(CH3)Rh(CO)2I3]−. This anion rapidly transforms, via the migration of a methyl group to an adjacent carbonyl ligand, affording the pentacoordinate acetyl complex [(CH3CO)Rh(CO)I3]−. This five-coordinate complex then reacts with carbon monoxide to form the six-coordinate dicarbonyl complex, which undergoes reductive elimination to release acetyl iodide (CH3C(O)I). The catalytic cycle involves two non-organometallic steps: conversion of methanol to methyl iodide and the hydrolysis of the acetyl iodide to acetic acid and hydrogen iodide. The reaction has


id: natural-gas-processing-20260505-0
file: data/en.wikipedia.org/wiki/Natural-gas_processing-0.md
category: reference
title: Natural-gas processing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Natural-gas_processing
date_saved: 2026-05-05T10:49:14.463304+00:00
instance: kb-cron
parent: natural-gas-processing-20260505-0
summary:
Natural-gas processing is a range of industrial processes designed to purify raw natural gas by removing contaminants such as solids, water, carbon dioxide (CO2), hydrogen sulfide (H2S), mercury and higher molecular mass hydrocarbons (condensate) to produce pipeline quality dry natural gas for pipeline distribution and final use. Some of the substances which contaminate natural gas have economic value and are further processed or sold. Hydrocarbons that are liquid at ambient conditions: temperature and pressure (i.e., pentane and heavier) are called natural-gas condensate (sometimes also called natural gasoline or simply condensate). Raw natural gas comes primarily from three types of wells: crude oil wells, gas wells, and condensate wells. Crude oil and natural gas are often found together in the same reservoir. Natural gas produced in wells with crude oil is generally classified as associated-dissolved gas as the gas had been associated with or dissolved in crude oil. Natural gas production not associated with crude oil is classified as “non-associated.” In 2009, 89 percent of U.S. wellhead production of natural gas was non-associated. Non-associated gas wells producing a dry gas in terms of condensate and water can send the dry gas directly to a pipeline or gas plant without undergoing any


id: natural-gas-processing-20260505-1
file: data/en.wikipedia.org/wiki/Natural-gas_processing-1.md
category: reference
title: Natural-gas processing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Natural-gas_processing
date_saved: 2026-05-05T10:49:14.463304+00:00
instance: kb-cron
parent: natural-gas-processing-20260505-0
summary:
Be free of particulate solids and liquid water to prevent erosion, corrosion or other damage to the pipeline. Be dehydrated of water vapor sufficiently to prevent the formation of methane hydrates within the gas processing plant or subsequently within the sales gas transmission pipeline. A typical water content specification in the U.S. is that gas must contain no more than seven pounds of water per million standard cubic feet of gas. In the UK this is defined as <-10 °C @ 85barg for entry into the NTS. Contain no more than trace amounts of components such as hydrogen sulfide, carbon dioxide, mercaptans, and nitrogen. The most common specification for hydrogen sulfide content is 0.25 grain H2S per 100 cubic feet of gas, or approximately 4 ppm. Specifications for CO2 typically limit the content to no more than two or three percent. In the UK hydrogen sulfide is specified ≤5 mg/m3 and total sulfur as ≤50 mg/m3, carbon dioxide as ≤2.0% (molar), and nitrogen as ≤5.0% (molar) for entry into the NTS. Maintain mercury at less than detectable limits (approximately 0.001 ppb by volume) primarily to avoid damaging equipment in the gas processing plant or the pipeline transmission system from mercury


id: natural-gas-processing-20260505-2
file: data/en.wikipedia.org/wiki/Natural-gas_processing-2.md
category: reference
title: Natural-gas processing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Natural-gas_processing
date_saved: 2026-05-05T10:49:14.463304+00:00
instance: kb-cron
parent: natural-gas-processing-20260505-0
summary:
Condensed liquid passes through a Joule-Thomson valve reducing the pressure to 20 bar and enters the demethanizer as the lower feed at -44.7 °C. Some of the vapour is routed through a turbo-expander and enters the demethanizer as the upper feed at -64 °C. The remaining vapor is chilled by the demethanizer overhead product and Joule-Thomson cooling (through a valve) and enters the column as reflux at -96 °C. The overhead product is mainly methane at 20 bar and -98 °C. This is heated and compressed to yield a sales gas at 20 bar and 40 °C. The bottom product is NGL at 20 barg which is fed to the deethanizer. The overhead product from the deethanizer is ethane and the bottoms are fed to the depropanizer. The overhead product from the depropanizer is propane and the bottoms are fed to the debutanizer. The overhead product from the debutanizer is a mixture of normal and iso-butane, and the bottoms product is a C5+ gasoline mixture. The operating conditions of the vessels in the NGL fractionation train are typically as follows. A typical composition of the feed and product is as follows. === Sweetening Units === The recovered streams of propane,


id: newbery-vautin-chlorination-process-20260505-0
file: data/en.wikipedia.org/wiki/Newbery–Vautin_chlorination_process-0.md
category: reference
title: Newbery–Vautin chlorination process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Newbery–Vautin_chlorination_process
date_saved: 2026-05-05T10:49:15.658889+00:00
instance: kb-cron
parent: newbery-vautin-chlorination-process-20260505-0
summary:
The Newbery–Vautin chlorination process is a method for extracting gold from its ore through the use of chlorination. This process was jointly developed by James Cosmo Newbery and Claude Theodore James Vautin. == Chlorination process == === History === A process for extracting gold from gold ores containing pyrite using chlorine gas was introduced by Karl Friedrich Plattner (1800–1858), around 1848. James Newbery and Claude Vautin began work on chlorination, at the United Pyrites Gold Extracting Co. in Bendigo, in 1878. They were awarded Victorian Patent No. 4484, in 1886, for their Newbery–Vautin chlorination process, which was faster than earlier chlorination processes. === Process description === Roasted gold-bearing pyrite concentrates and water were combined in a barrel, to which calcium chloride and sulphuric acid were added. The barrel was then made airtight. Compressed air was used to raise the internal pressure to four atmospheres, and the barrel was set in rotation. The sulphuric acid and calcium chloride reacted to form chlorine gas. The gold contained in the concentrate reacted with the chlorine to form gold chloride, which is a salt soluble in water. Once the extraction had occurred—after around four hours—the liquid containing the gold chloride was separated from the


id: nitrophosphate-process-20260505-0
file: data/en.wikipedia.org/wiki/Nitrophosphate_process-0.md
category: reference
title: Nitrophosphate process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nitrophosphate_process
date_saved: 2026-05-05T10:49:16.886778+00:00
instance: kb-cron
parent: nitrophosphate-process-20260505-0
summary:
The nitrophosphate process (also known as the Odda process) is a method for the industrial production of nitrogen fertilizers invented by Erling Johnson in Odda Municipality, Norway. around 1927. The process involves acidifying phosphate rock with dilute nitric acid to produce a mixture of phosphoric acid and calcium nitrate. Ca 5 ( PO 4 ) 3 OH + 10 HNO 3 ⟶ 3 H 3 PO 4 + 5 Ca ( NO 3 ) 2 + H 2 O {\displaystyle {\ce {Ca5(PO4)3OH + 10 HNO3 -> 3 H3PO4 + 5 Ca(NO3)2 + H2O}}} The mixture is cooled to below 0 °C, where the calcium nitrate crystallizes and can be separated from the phosphoric acid. 2 H 3 PO 4 + 3 Ca ( NO 3 ) 2 + 12 H 2 O ⟶ 2 H 3 PO 4 + 3 Ca ( NO 3 ) 2 ⋅ 4 H 2 O {\displaystyle {\ce {2 H3PO4 + 3 Ca(NO3)2 + 12 H2O -> 2 H3PO4 + 3 Ca(NO3)2.4H2O}}} The resulting calcium nitrate produces nitrogen fertilizer. The filtrate is composed mainly of phosphoric acid with some nitric acid and traces of calcium nitrate, and this is neutralized with ammonia to produce a


id: oil-refinery-20260505-0
file: data/en.wikipedia.org/wiki/Oil_refinery-0.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefied petroleum gas and petroleum naphtha. Petrochemical feedstock like ethylene and propylene can also be produced directly by cracking crude oil without the need of using refined products of crude oil such as naphtha. The crude oil feedstock has typically been processed by an oil production plant. There is usually an oil depot at or near an oil refinery for the storage of incoming crude oil feedstock as well as bulk liquid products. In 2020, the total capacity of global refineries for crude oil was about 101.2 million barrels per day. Oil refineries are typically large, sprawling industrial complexes with extensive piping running throughout, carrying streams of fluids between large chemical processing units, such as distillation columns. In many ways, oil refineries use many different technologies and can be thought of as types of chemical plants. Since December 2008, the world's largest oil refinery has been the Jamnagar Refinery owned by Reliance Industries, located in Gujarat, India, with a processing capacity of 1.24 million barrels (197,000


id: oil-refinery-20260505-1
file: data/en.wikipedia.org/wiki/Oil_refinery-1.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
== History == The Chinese were among the first civilizations to refine oil. As early as the first century, the Chinese were refining crude oil for use as an energy source. Between 512 and 518, in the late Northern Wei dynasty, the Chinese geographer, writer and politician Li Daoyuan introduced the process of refining oil into various lubricants in his famous work Commentary on the Water Classic. Crude oil was often distilled by Persian chemists, with clear descriptions given in handbooks such as those of Muhammad ibn Zakarīya Rāzi (c. 865–925). The streets of Baghdad were paved with tar, derived from petroleum that became accessible from natural fields in the region. In the 9th century, oil fields were exploited in the area around modern Baku, Azerbaijan. These fields were described by the Arab geographer Abu al-Hasan 'Alī al-Mas'ūdī in the 10th century, and by Marco Polo in the 13th century, who described the output of those wells as hundreds of shiploads. Arab and Persian chemists also distilled crude oil in order to produce flammable products for military purposes. Through Islamic Spain, distillation became available in Western Europe by the 12th century. In the Northern Song dynasty (960–1127), a workshop called


id: oil-refinery-20260505-2
file: data/en.wikipedia.org/wiki/Oil_refinery-2.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
In the United States, for various complex economic and political reasons, the construction of new refineries came to a virtual stop in about the 1980s. However, many of the existing refineries in the United States have revamped many of their units and/or constructed add-on units in order to: increase their crude oil processing capacity, increase the octane rating of their product gasoline, lower the sulfur content of their diesel fuel and home heating fuels to comply with environmental regulations and comply with environmental air pollution and water pollution requirements. === United States === In the 19th century, refineries in the U.S. processed crude oil primarily to recover the kerosene. There was no market for the more volatile fraction, including gasoline, which was considered waste and was often dumped directly into the nearest river. The invention of the automobile shifted demand to gasoline and diesel, which remain the primary refined products today. Today, national and state legislation require refineries to meet stringent air and water cleanliness standards. In fact, oil companies in the U.S. perceive obtaining a permit to build a modern refinery to be so difficult and costly that no new refineries were built (though many have been expanded) in


id: oil-refinery-20260505-3
file: data/en.wikipedia.org/wiki/Oil_refinery-3.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
Petroleum products are materials derived from crude oil (petroleum) as it is processed in oil refineries. The majority of petroleum is converted to petroleum products, which includes several classes of fuels. Oil refineries also produce various intermediate products such as hydrogen, light hydrocarbons, reformate and pyrolysis gasoline. These are not usually transported but instead are blended or processed further on-site. Chemical plants are thus often adjacent to oil refineries or a number of further chemical processes are integrated into it. For example, light hydrocarbons are steam-cracked in an ethylene plant, and the produced ethylene is polymerized to produce polyethene. To ensure both proper separation and environmental protection, a very low sulfur content is necessary in all but the heaviest products. The crude sulfur contaminant is transformed to hydrogen sulfide via catalytic hydrodesulfurization and removed from the product stream via amine gas treating. Using the Claus process, hydrogen sulfide is afterward transformed to elementary sulfur to be sold to the chemical industry. The rather large heat energy freed by this process is directly used in the other parts of the refinery. Often an electrical power plant is combined into the whole refinery process to take up the excess heat. According to


id: oil-refinery-20260505-4
file: data/en.wikipedia.org/wiki/Oil_refinery-4.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
Desalter unit washes out salt, and other water-soluble contaminants, from the crude oil before it enters the atmospheric distillation unit. Pre-flash and/or pre-distillation which is found in most atmospheric crude oil units of more than 100,000 bpsd in capacity. Crude oil distillation unit distills the incoming crude oil into various fractions for further processing in other units. See continuous distillation. Vacuum distillation further distills the residue oil from the bottom of the crude oil distillation unit. The vacuum distillation is performed at a pressure well below atmospheric pressure. Naphtha hydrotreater unit uses hydrogen to desulfurize naphtha from atmospheric distillation. Naphtha must be desulfurized before sending it to a catalytic reformer unit. Catalytic reformer converts the desulfurized naphtha molecules into higher-octane molecules to produce reformate (reformer product). The reformate has higher content of aromatics and cyclic hydrocarbons which is a component of the end-product gasoline or petrol. An important byproduct of a reformer is hydrogen released during the catalyst reaction. The hydrogen is used either in the hydrotreaters or the hydrocracker. Distillate hydrotreater desulfurizes distillates (such as diesel) after atmospheric distillation. Uses hydrogen to desulfurize the naphtha fraction from the crude oil distillation or other units within the refinery. Distillate hydrotreaters


id: oil-refinery-20260505-5
file: data/en.wikipedia.org/wiki/Oil_refinery-5.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
== Crude oil distillation unit == The crude oil distillation unit (CDU) is the first processing unit in virtually all petroleum refineries. The CDU distills the incoming crude oil into various fractions of different boiling ranges, each of which is then processed further in the other refinery processing units. The CDU is often referred to as the atmospheric distillation unit because it operates at slightly above atmospheric pressure. Below is a schematic flow diagram of a typical crude oil distillation unit. The incoming crude oil is preheated by exchanging heat with some of the hot, distilled fractions and other streams. It is then desalted to remove inorganic salts (primarily sodium chloride). Following the desalter, the crude oil is further heated by exchanging heat with some of the hot, distilled fractions and other streams. It is then heated in a fuel-fired furnace (fired heater) to a temperature of about 398 °C and routed into the bottom of the distillation unit. The cooling and condensing of the distillation tower overhead is provided partially by exchanging heat with the incoming crude oil and partially by either an air-cooled or water-cooled condenser. Additional heat is removed from the distillation column by a pumparound system


id: oil-refinery-20260505-6
file: data/en.wikipedia.org/wiki/Oil_refinery-6.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
=== Background === Modern petroleum refining involves a complicated system of interrelated chemical reactions that produce a wide variety of petroleum-based products. Many of these reactions require precise temperature and pressure parameters. The equipment and monitoring required to ensure the proper progression of these processes is complex, and has evolved through the advancement of the scientific field of petroleum engineering. The wide array of high pressure and/or high temperature reactions, along with the necessary chemical additives or extracted contaminants, produces an astonishing number of potential health hazards to the oil refinery worker. Through the advancement of technical chemical and petroleum engineering, the vast majority of these processes are automated and enclosed, thus greatly reducing the potential health impact to workers. However, depending on the specific process in which a worker is engaged, as well as the particular method employed by the refinery in which he/she works, significant health hazards remain. Although occupational injuries in the United States were not routinely tracked and reported at the time, reports of the health impacts of working in an oil refinery can be found as early as the 1800s. For instance, an explosion in a Chicago refinery killed 20 workers in 1890. Since then,


id: oil-refinery-20260505-7
file: data/en.wikipedia.org/wiki/Oil_refinery-7.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
=== Hazard controls === The theory of hierarchy of controls can be applied to petroleum refineries and their efforts to ensure worker safety. Elimination and substitution are unlikely in petroleum refineries, as many of the raw materials, waste products, and finished products are hazardous in one form or another (e.g. flammable, carcinogenic). Examples of engineering controls include a fire detection/extinguishing system, pressure/chemical sensors to detect/predict loss of structural integrity, and adequate maintenance of piping to prevent hydrocarbon-induced corrosion (leading to structural failure). Other examples employed in petroleum refineries include the post-construction protection of steel components with vermiculite to improve heat/fire resistance. Compartmentalization can help to prevent a fire or other systems failure from spreading to affect other areas of the structure, and may help prevent dangerous reactions by keeping different chemicals separate from one another until they can be safely combined in the proper environment. Administrative controls include careful planning and oversight of the refinery cleaning, maintenance, and turnaround processes. These occur when many of the engineering controls are shut down or suppressed and may be especially dangerous to workers. Detailed coordination is necessary to ensure that maintenance of one part of the facility will not cause dangerous exposures to


id: oil-refinery-20260505-8
file: data/en.wikipedia.org/wiki/Oil_refinery-8.md
category: reference
title: Oil refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oil_refinery
date_saved: 2026-05-05T10:49:18.084931+00:00
instance: kb-cron
parent: oil-refinery-20260505-0
summary:
Corrosion of metallic components is a major factor of inefficiency in the refining process. Because it leads to equipment failure, it is a primary driver for the refinery maintenance schedule. Corrosion-related direct costs in the U.S. petroleum industry as of 1996 were estimated at US$3.7 billion. Corrosion occurs in various forms in the refining process, such as pitting corrosion from water droplets, embrittlement from hydrogen, and stress corrosion cracking from sulfide attack. From a materials standpoint, carbon steel is used for upwards of 80 percent of refinery components, which is beneficial due to its low cost. Carbon steel is resistant to the most common forms of corrosion, particularly from hydrocarbon impurities at temperatures below 205 °C, but other corrosive chemicals and environments prevent its use everywhere. Common replacement materials are low alloy steels containing chromium and molybdenum, with stainless steels containing more chromium dealing with more corrosive environments. More expensive materials commonly used are nickel, titanium, and copper alloys. These are primarily saved for the most problematic areas where extremely high temperatures and/or very corrosive chemicals are present. Corrosion is fought by a complex system of monitoring, preventative repairs, and careful use of materials. Monitoring methods include both offline checks


id: olin-raschig-process-20260505-0
file: data/en.wikipedia.org/wiki/Olin_Raschig_process-0.md
category: reference
title: Olin Raschig process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Olin_Raschig_process
date_saved: 2026-05-05T10:49:19.318530+00:00
instance: kb-cron
parent: olin-raschig-process-20260505-0
summary:
The Olin Raschig process is a chemical process for the production of hydrazine. The main steps in this process, patented by German chemist Friedrich Raschig in 1906 and one of three reactions named after him, are the formation of monochloramine from ammonia and hypochlorite, and the subsequent reaction of monochloramine with ammonia towards hydrazine. The process was further optimised and used by the Olin Corporation for the production of anhydrous hydrazine for aerospace applications. == Process == The commercially used Olin Raschig process consists of the following steps: First, sodium hypochlorite solution is mixed with a threefold excess of ammonia at 5 °C to give monochloramine. The primary reaction proceeds according to the idealised equation NaOCl + NH3 → NH2Cl + NaOH The monochloramine solution is then added to a 30-fold excess of ammonia at 130 °C and elevated pressure, causing a second reaction NH2Cl + NH3 → N2H4 + HCl The hydrochloric acid and sodium hydroxide byproducts undergo a secondary reaction to release the byproducts of water and sodium chloride. The overall reaction is thus NaOCl + 2NH3 → N2H4 + NaCl + H2O Excess ammonia and sodium chloride are removed by distillation, followed by azeotropic distillation with aniline


id: omega-process-20260505-0
file: data/en.wikipedia.org/wiki/OMEGA_process-0.md
category: reference
title: OMEGA process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/OMEGA_process
date_saved: 2026-05-05T10:49:20.520442+00:00
instance: kb-cron
parent: omega-process-20260505-0
summary:
The OMEGA process ("Only MEG Advantage") is a chemical process discovered by the Shell Global Solutions company that is used to produce ethylene glycol from ethylene. This process comprises two steps, the controlled oxidation of ethylene to ethylene oxide, and the net hydrolysis of ethylene oxide to monoethylene glycol (MEG). The first chemical plant using the OMEGA process was started in South Korea. Subsequent OMEGA plants have been started in Saudi Arabia and Singapore. Shell claims that this process, compared to conventional ones, does not produce higher glycols, uses less steam and water, and generates less waste. == Ethylene oxidation == To produce ethylene oxide, ethylene is oxidized with dioxygen in the presence of a silver catalyst. Some ethylene is over-oxidized to carbon dioxide and water, which is wasteful; early processes only gave ~ 65% selectivity for ethylene oxide as a result. In the OMEGA process, over-oxidation is reduced by including ethyl chloride as a moderator. == Ethylene oxide hydrolysis == Conventionally, monoethylene glycol (HOC2H4OH) is produced by the controlled hydrolysis of ethylene oxide (C2H4O). The monoethylene glycol product is also able to react with ethylene oxide to give diethylene glycol, and so on; sequential reaction with ethylene oxide is


id: organosolv-20260505-0
file: data/en.wikipedia.org/wiki/Organosolv-0.md
category: reference
title: Organosolv
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Organosolv
date_saved: 2026-05-05T10:49:21.669767+00:00
instance: kb-cron
parent: organosolv-20260505-0
summary:
In industrial paper-making processes, organosolv is a pulping technique that uses an organic solvent to solubilise lignin and hemicellulose. It has been considered in the context of both pulp and paper manufacture and biorefining for subsequent conversion of cellulose to fuel ethanol. The process was invented by Theodor Kleinert in 1968 as an environmentally benign alternative to kraft pulping. Organosolv has several advantages when compared to other popular methods such as kraft or sulfite pulping. In particular, the ability to obtain relatively high quality lignin adds value to a process stream otherwise considered as waste. Organosolv solvents are easily recovered by distillation, leading to less water pollution and elimination of the odour usually associated with kraft pulping. == Solvents == Organosolv pulping involves contacting a lignocellulosic feedstock such as chipped wood with an aqueous organic solvent at temperatures ranging from 140 to 220 °C. This causes lignin to break down by hydrolytic cleavage of alpha aryl-ether links into fragments that are soluble in the solvent system. Solvents used include acetone, methanol, ethanol, butanol, ethylene glycol, formic acid, and acetic acid. The concentration of solvent in water ranges from 40 to 80%. Higher boiling solvents have the advantage of a lower


id: organosolv-20260505-1
file: data/en.wikipedia.org/wiki/Organosolv-1.md
category: reference
title: Organosolv
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Organosolv
date_saved: 2026-05-05T10:49:21.669767+00:00
instance: kb-cron
parent: organosolv-20260505-0
summary:
=== Chempolis process === Chempolis Ltd in Oulu, Finland has developed, since 1995, a process concept where any lignocellulosic fibrous biomass sources are delignified with formic acid (biosolvent) in a compact process. The so-called "formico" technology incorporates full biosolvent recovery by evaporation and distillation in order to have a closed-loop process with minimal water need and effluent discharge. The delignification selectively fractionates lignocellulose components into cellulosic fibre, hemicellulose and lignin. Part of the hemicelluloses react to furfural and acetic acid, which are recovered in the distillation process to high-grade commercial products. The clean cellulosic fibre is used in various high-end packaging and textile purposes (bleached easily with hydrogen peroxide), or hydrolysed into high-purity glucose readily converted into biochemicals, or the glucose is easily fermented to bioethanol. The dissolved hemicelluloses and lignin after delignification are concentrated in evaporation and separated to produce hemicellulose fraction suitable for fermentation into ethanol or conversion to biochemicals. The separated lignin is sulfur-free and used in high-end applications replacing fossil aromatics. === American Science and Technology (AST) process === American Science and Technology (AST) based out of Chicago, Illinois, USA, has developed a process which uses a patented second generation Organosolv process to convert any kind


id: osmotic-dehydration-20260505-0
file: data/en.wikipedia.org/wiki/Osmotic_dehydration-0.md
category: reference
title: Osmotic dehydration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Osmotic_dehydration
date_saved: 2026-05-05T10:49:22.820567+00:00
instance: kb-cron
parent: osmotic-dehydration-20260505-0
summary:
Osmotic dehydration is an operation used for the partial removal of water from plant tissues by immersion in a hypertonic (osmotic) solution. Sugar or salt solutions are used to reduce the moisture content of foods before actual drying process. This technique is used to give the product quality improvement over conventional drying process. Mild heat treatment after osmotic dehydration favours colour and flavour retention resulting in the product having superior organoleptic characteristics. It also increases resistance to heat treatment, prevents enzymatic browning and inhibits activities of polyphenol oxidase. The process is economical. Osmotic dehydration depends on: Temperature of osmotic solution. Concentration of the osmotic solution. Osmotic agent used. Process duration. Geometry of food material. David Baszucki == Process == Water removal is based on the natural and non-destructive phenomenon of osmosis across cell membranes. The driving force for the diffusion of water from the tissue into the solution is provided by the higher osmotic pressure of the hyper-tonic solution. The diffusion of water is accompanied by the simultaneous counter diffusion of solutes from the osmotic solution into the tissue. Since the cell membrane responsible for osmotic transport is not perfectly selective, solutes present in the cells (organic acids, reducing sugars,


id: ostwald-process-20260505-0
file: data/en.wikipedia.org/wiki/Ostwald_process-0.md
category: reference
title: Ostwald process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ostwald_process
date_saved: 2026-05-05T10:49:38.930345+00:00
instance: kb-cron
parent: ostwald-process-20260505-0
summary:
The Ostwald process is a chemical process used for making nitric acid (HNO3). The Ostwald process is a mainstay of the modern chemical industry, and it provides the main raw material for the most common type of fertilizer production. Historically and practically, the Ostwald process is closely associated with the Haber process, which provides the requisite raw material, ammonia (NH3). This method is preferred over other methods of nitric acid production because it is less expensive and more efficient. == Reactions == Ammonia is converted to nitric acid in 2 stages. === Initial oxidation of ammonia === The Ostwald process begins with burning ammonia. Ammonia burns in oxygen at temperature about 900 °C (1,650 °F) and pressure up to 8 standard atmospheres (810 kPa) in the presence of a catalyst such as platinum gauze, alloyed with 10% rhodium to increase its strength and nitric oxide yield, platinum metal on fused silica wool, copper, or nickel to form nitric oxide (nitrogen(II) oxide) and water (as steam). This reaction is strongly exothermic, making it a useful heat source once initiated: 4NH3 + 5O2 → 4NO + 6H2O (ΔH = −905.2 kJ/mol) ==== Side reactions ==== A number of side reactions compete with


id: oxfa-process-20260505-0
file: data/en.wikipedia.org/wiki/OxFA_process-0.md
category: reference
title: OxFA process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/OxFA_process
date_saved: 2026-05-05T10:49:40.132912+00:00
instance: kb-cron
parent: oxfa-process-20260505-0
summary:
The OxFA process is a process to produce formic acid from biomass by catalytic oxidation using molecular oxygen or air. Polyoxometalates of the Keggin-type are used as catalysts. == OxFA-Process == === General description === Formic acid is obtained by aqueous catalytic partial oxidation of wet biomass. A Keggin-type polyoxometalate (H5PV2Mo10O40) is used as the homogeneous catalyst to convert sugars, wood, waste paper or cyanobacteria to formic acid and CO2 as the sole byproduct. Yields of up to 53% formic acid can be achieved. It is possible to convert water-insoluble biomass in a suspension with the catalyst. After the reaction, formic acid is separated from the reaction mixture. Depending on the separation process, the formic acid can be further purified or used as it is. The remaining solution of the catalyst, residual formic acid and additives are recycled to the reaction. In this step, solids (e.g. soil from dirty biomass) or unreactive inorganics (e.g. inorganic salts from the natural salt content of the biomass) may be separated from the catalyst solution. The general reaction for a simple sugar like glucose can be summarized as follows: C6H12O6 + wO2 → xHCOOH + yCO2 + zH2O === Biomass pretreatment === Water-insoluble biomass


id: paper-chemicals-20260505-0
file: data/en.wikipedia.org/wiki/Paper_chemicals-0.md
category: reference
title: Paper chemicals
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Paper_chemicals
date_saved: 2026-05-05T10:49:41.282318+00:00
instance: kb-cron
parent: paper-chemicals-20260505-0
summary:
Paper chemicals designate a group of chemicals that are used for paper manufacturing, or modify the properties of paper. These chemicals can be used to alter the paper in many ways, including changing its color and brightness, or by increasing its strength and resistance to water. The chemicals can be defined on basis of their usage in the process. Chemical usage is not only for imparting properties to paper but to handle the water cycles in the process, conditioning of fabrics, cleaning of equipment and several other applications. == Chemicals used in paper manufacturing == == Pulping == Chemical pulping involves dissolving lignin in order to extract the cellulose from the wood fiber. The different processes of chemical pulping include the Kraft process, which uses caustic soda and sodium sulfide and is the most common; alternatively, the use of sulfurous acid is known as the sulfite process, the neutral sulfite semichemical is treated as a third process separate from sulfite, and soda pulping which is the least ecologically hazardous utilizing sodium hydroxide or anthraquinone. Caustic soda is added to increase the pH in the pulping process of fibers. The higher pH of the paper-fiber solution causes the fibers to smoothen


id: paraffin-oxidation-20260505-0
file: data/en.wikipedia.org/wiki/Paraffin_oxidation-0.md
category: reference
title: Paraffin oxidation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Paraffin_oxidation
date_saved: 2026-05-05T10:49:42.439928+00:00
instance: kb-cron
parent: paraffin-oxidation-20260505-0
summary:
Paraffin oxidation is a historical industrial process for the production of synthetic fatty acids. The fatty acids are further processed to consumer products such as soaps and fats as well as to lubricating greases for technical applications. Coal slack wax, a saturated, high molecular weight hydrocarbon mixture and by-product of the Fischer–Tropsch process was used as raw material. Side products were a wide range of carboxylic acids and oxidation products such as alcohols, aldehydes, esters, or ketones. The oxidation of paraffins was carried out in the liquid phase by molecular oxygen, e.g. by aerating with oxygen or atmospheric air, in the presence of catalysts such as permanganates, e.g. 0.1% - 0.3% potassium permanganate, at temperatures in the range of about 100 to 120 °C and under atmospheric pressure. == History == The process was commercially important from the mid-1930s on and was carried out until the first years after the Second World War on a large industrial scale. Paraffin oxidation enabled for first time the large-scale production of synthetic butter from coal by chemical means which was at that time seen as a sensation. Because of the high availability of inexpensive natural fats and the competition by petroleum-based fatty alcohols,


id: pechini-process-20260505-0
file: data/en.wikipedia.org/wiki/Pechini_process-0.md
category: reference
title: Pechini process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pechini_process
date_saved: 2026-05-05T10:49:43.636561+00:00
instance: kb-cron
parent: pechini-process-20260505-0
summary:
The Pechini process or liquid mix process as proposed in 1967 is a technique of depositing dielectric films of titanates and niobates of lead and alkaline-earth elements in the production of capacitors. Later, the process was customised for the in-lab synthesis of multicomponent finely dispersed oxide materials. It is named after its American inventor, Maggio Pechini. == Description == It is related to the sol-gel route. An aqueous solution of suitable oxides or salts is mixed with an alpha hydroxycarboxylic acid such as citric acid. Chelation takes place in the solution. A polyhydroxy alcohol is then added, and the liquid is heated to 150–250 °C (300–480 °F) to allow the chelates to polymerize, or form large, cross-linked networks. As excess water is removed by heating, a solid polymeric resin results. Eventually, at still higher temperatures of 500–900 °C (930–1,650 °F), the resin is decomposed or charred, and ultimately a mixed oxide is obtained. Particle size is extremely small, typically 20 to 50 nanometres (although there is agglomeration of these particles into larger clusters), with intimate mixing taking place on the atomic scale. == Uses == This method has been used for synthesizing over 100 mixed metal oxides including lanthanum manganite


id: pedersen-process-20260505-0
file: data/en.wikipedia.org/wiki/Pedersen_process-0.md
category: reference
title: Pedersen process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pedersen_process
date_saved: 2026-05-05T10:49:44.805341+00:00
instance: kb-cron
parent: pedersen-process-20260505-0
summary:
The Pederson process is a process of refining aluminum that first separates iron by reducing it to metal, and reacting alumina with lime to produce calcium aluminate, which is then leached with sodium hydroxide. It is more environmentally friendly than the more well-known Bayer process. This is because instead of producing alumina slag, also known as red mud, it produces pig iron as a byproduct. Red mud is considered both an economic and environmental challenge in the aluminum industry because it is considered a waste, with little benefit. It destroys the environment with its high pH, and is costly to maintain, even when in a landfill. Iron, however, is used in the manufacture of steel, and has structural uses in civil engineering and chemical uses as a catalyst. == History == The Pedersen process was invented by Harald Pedersen in the 1920s and used in Norway for over 40 years before shutting down due to the Pedersen process being less economically competitive than the Bayer process. However, it is believed a modern Pedersen process could be economically viable with "low-quality" bauxite, as even though "low-quality" bauxite has less alumina in the form of trihydrate gibbsite, it has more iron oxide


id: penex-20260505-0
file: data/en.wikipedia.org/wiki/Penex-0.md
category: reference
title: Penex
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Penex
date_saved: 2026-05-05T10:49:45.977817+00:00
instance: kb-cron
parent: penex-20260505-0
summary:
The Penex process is a continuous catalytic process used in the refining of crude oil. It isomerizes light naphtha (C5/C6) into higher-octane, branched C5/C6 molecules. It also reduces the concentration of benzene in the gasoline pool. It was first used commercially in 1958. Ideally, the isomerization catalyst converts normal pentane (nC5) to isopentane (iC5) and normal hexane (nC6) to 2,2- and 2,3-dimethylbutane. The thermodynamic equilibrium is more favorable at low temperature. == Background == In the petroleum industry, much research has been done on the upgrading of light hydrocarbons. The realisation that normal pentane is one of the most important remaining components of naphtha that can be easily upgraded prompted Phillips Petroleum to investigate the various processes for converting normal (linear) pentane into (branched) isopentane. The decisive factor in the isomerisation of normal pentane is an increase in the total octane number. This improvement in quality makes the result more valuable for blending with today's high-octane fuels. In addition, like other isoparaffins, isopentane has a low sensitivity (research octane minus engine octane) which means improved performance at street octane. Increasing the octane number also allows larger quantities of pentanes to be blended into premium petrol. In a refinery, light naphtha


id: peroxide-process-20260505-0
file: data/en.wikipedia.org/wiki/Peroxide_process-0.md
category: reference
title: Peroxide process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Peroxide_process
date_saved: 2026-05-05T10:49:47.106497+00:00
instance: kb-cron
parent: peroxide-process-20260505-0
summary:
The peroxide process is a method for the industrial production of hydrazine. In this process hydrogen peroxide is used as an oxidant instead of sodium hypochlorite, which is traditionally used to generate hydrazine. The main advantage of the peroxide process to hydrazine relative to the traditional Olin Raschig process is that it does not coproduce salt. In this respect, the peroxide process is an example of green chemistry. Since many millions of kilograms of hydrazine are produced annually, this method is of both commercial and environmental significance. == Production == === Ketazine formation === In the usual implementation, hydrogen peroxide is used together with acetamide. This mixture does not react with ammonia directly but does so in the presence of methyl ethyl ketone to give the oxaziridine. Balanced equations for the individual steps are as follows. Imine formation through condensation: Me(Et)C=O + NH3 → Me(Et)C=NH + H2O Oxidation of the imine to the oxaziridine: Me(Et)C=NH + H2O2 → Me(Et)CONH + H2O Condensation of the oxaziridine with a second molecule of ammonia to give the hydrazone: Me(Et)CONH + NH3 → Me(Et)C=NNH2 + H2O The hydrazone then condenses with a second equivalent of ketone to give the ketazine: Me(Et)C=O + Me(Et)C=NNH2 →


id: petersen-matrix-20260505-0
file: data/en.wikipedia.org/wiki/Petersen_matrix-0.md
category: reference
title: Petersen matrix
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Petersen_matrix
date_saved: 2026-05-05T10:49:48.296158+00:00
instance: kb-cron
parent: petersen-matrix-20260505-0
summary:
The Petersen matrix is a comprehensive description of systems of biochemical reactions used to model reactors for pollution control (engineered decomposition) as well as in environmental systems. It has as many columns as the number of relevant involved components (chemicals, pollutants, biomasses, gases) and as many rows as the number of involved processes (biochemical reactions and physical degradation). One further column is added to host the description of the kinetics of each transformation (rate equation). == Matrix structure == The mass conservation principle for each process is expressed in the rows of the matrix. If all components are included (none omitted) then the mass conservation principle states that, for each process: for all process i : ∑ j = 1 n a i j ρ j ˙ = 0 , {\displaystyle {\text{for all process }}i:\sum _{j=1}^{n}a_{ij}{\dot {\rho _{j}}}=0\;,} where ρ j ˙ {\displaystyle {\dot {\rho _{j}}}} is the density rate of each component. This can also be seen as the process stoichiometric relation. Moreover, the rate of variation of each component for all processes simultaneous effect can be easily assessed by summing the columns: for all component j : ∂ C j ∂ t = ∑ i = 1 m


id: phosphorolysis-20260505-0
file: data/en.wikipedia.org/wiki/Phosphorolysis-0.md
category: reference
title: Phosphorolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Phosphorolysis
date_saved: 2026-05-05T10:49:49.491683+00:00
instance: kb-cron
parent: phosphorolysis-20260505-0
summary:
Phosphorolysis is the cleavage of a compound in which inorganic phosphate is the attacking group. It is analogous to hydrolysis. An example of this is glycogen breakdown by glycogen phosphorylase, which catalyzes attack by inorganic phosphate on the terminal glycosyl residue at the nonreducing end of a glycogen molecule. If the glycogen chain has n glucose units, the products of a single phosphorolytic event are one molecule of glucose 1-phosphate and a glycogen chain of n-1 remaining glucose units. In addition, sometimes phosphorolysis is preferable to hydrolysis (like in the breakdown of glycogen or starch, as in the example above) because glucose 1-phosphate yields more ATP than does free glucose when subsequently catabolized to pyruvate. Another example of phosphorolysis is seen in the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate in glycolysis. The mechanism involves phosphorolysis. == See also == Phosphorylase == References == == External links == Media related to Phosphorolysis at Wikimedia Commons


id: photochlorination-20260505-0
file: data/en.wikipedia.org/wiki/Photochlorination-0.md
category: reference
title: Photochlorination
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photochlorination
date_saved: 2026-05-05T10:49:50.686369+00:00
instance: kb-cron
parent: photochlorination-20260505-0
summary:
Photochlorination is a chlorination reaction that is initiated by light. Usually a C-H bond is converted to a C-Cl bond. Photochlorination is carried out on an industrial scale. The process is exothermic and proceeds as a chain reaction initiated by the homolytic cleavage of molecular chlorine into chlorine radicals by ultraviolet radiation. Many chlorinated solvents are produced in this way. == History == Chlorination is one of the oldest known substitution reactions in chemistry. The French chemist Jean-Baptiste Dumas investigated the substitution of hydrogen for chlorine by acetic acid in candle wax as early as 1830. He showed that for each mole of chlorine introduced into a hydrocarbon, one mole of hydrogen chloride is also formed and noted the light-sensitivity of this reaction. The idea that these reactions might be chain reactions is attributed to Max Bodenstein (1913). He assumed that in the reaction of two molecules not only the end product of the reaction can be formed, but also unstable, reactive intermediates which can continue the chain reaction. Photochlorination garnered commercial attention with the availability of cheap chlorine from chloralkali electrolysis. Chlorinated alkanes found an initial application in pharyngeal sprays. These contained chlorinated alkanes in relatively large quantities as


id: photochlorination-20260505-1
file: data/en.wikipedia.org/wiki/Photochlorination-1.md
category: reference
title: Photochlorination
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photochlorination
date_saved: 2026-05-05T10:49:50.686369+00:00
instance: kb-cron
parent: photochlorination-20260505-0
summary:
=== Chloromethanes === An example of photochlorination at low temperatures and under ambient pressure is the chlorination of chloromethane to dichloromethane. The liquefied chloromethane (boiling point -24 °C) is mixed with chlorine in the dark and then irradiated with a mercury-vapor lamp. The resulting dichloromethane has a boiling point of 41 °C and is later separated by distillation from methyl chloride. The photochlorination of methane has a lower quantum yield than the chlorination of dichloromethane. Due to the high light intensity required, the intermediate products are directly chlorinated, so that mainly tetrachloromethane is formed. === Chlorinated paraffins === A major application of photochlorination is the production of chloroparaffins. Mixtures of complex composition consisting of several chlorinated paraffins are formed. Chlorinated paraffins have the general sum formula CxH(2x−y+2)Cly and are categorized into three groups: Low molecular weight chlorinated paraffins are short chain chloroparaffins (SCCP) with 10 to 13 carbon atoms, followed by medium chain chloroparaffins (MCCP) with carbon chain lengths of 14 to 17 carbon atoms and long chain chlorinated paraffins (LCCP), owing a carbon chainwith more than 17 carbon atoms. Approximately 70% of the chloroparaffins produced are MCCPs with a degree of chlorination from 45 to 52%. The remaining 30%


id: photochlorination-20260505-2
file: data/en.wikipedia.org/wiki/Photochlorination-2.md
category: reference
title: Photochlorination
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photochlorination
date_saved: 2026-05-05T10:49:50.686369+00:00
instance: kb-cron
parent: photochlorination-20260505-0
summary:
== Further reading == H. Hartig: Einfache Dimensionierung, photochemischer Reaktoren. In: Chemie Ingenieur Technik – CIT. 42, 1970, p. 1241–1245, doi:10.1002/cite.330422002. Dieter Wöhrle, Michael W. Tausch, Wolf-Dieter Stohrer: Photochemie: Konzepte, Methoden, Experimente. Wiley & Sons, 1998, ISBN 978-3-527-29545-6, p. 271–275. US Grant 1379367, F. Sparre & W. E. Masland, "Process of Chlorination", issued 1921-05-24, assigned to Du Pont US Grant 1459777, R. Leiser & F. Ziffer, "Process and Apparatus for the Chlorination of Methane", issued 1920-02-14, assigned to Ziffer Fritz and Leiser Richard David A. Mixon, Michael P. Bohrer, Patricia A. O’Hara: Ultrapurification of SiCl4 by photochlorination in a bubble column reactor. In: AIChE Journal. 36, 1990, p. 216–226, doi:10.1002/aic.690360207. Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, p. 71, ISBN 0-12-352651-5 Hans Von Halban: Die Lichtabsorption des Chlors. In: Zeitschrift für Elektrochemie und angewandte physikalische Chemie. 28, 1922, p. 496–499, doi:10.1002/bbpc.19220282304. Arthur John Allmand: Part I.—Einstein’s law of photochemical equivalence. Introductory address to Part I. In: Trans. Faraday Soc. 21, 1926, p. 438, doi:10.1039/TF9262100438. Marion L. Sharrah, Geo. C. Feighner: Synthesis of Dodecylbenzen – Synthetic Detergent Intermediate. In: Industrial & Engineering Chemistry. 46, 1954, p.


id: photoelectrochemical-reduction-of-carbon-dioxide-20260505-0
file: data/en.wikipedia.org/wiki/Photoelectrochemical_reduction_of_carbon_dioxide-0.md
category: reference
title: Photoelectrochemical reduction of carbon dioxide
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoelectrochemical_reduction_of_carbon_dioxide
date_saved: 2026-05-05T10:49:51.841362+00:00
instance: kb-cron
parent: photoelectrochemical-reduction-of-carbon-dioxide-20260505-0
summary:
Photoelectrochemical reduction of carbon dioxide, also known as photoelectrolysis of carbon dioxide, is a chemical process whereby carbon dioxide is reduced to carbon monoxide or hydrocarbons by the energy of incident light. This process requires catalysts, most of which are semiconducting materials. The feasibility of this chemical reaction was first theorised by Giacomo Luigi Ciamician, an Italian photochemist. Already in 1912 he stated that "[b]y using suitable catalyzers, it should be possible to transform the mixture of water and carbon dioxide into oxygen and methane, or to cause other endo-energetic processes." Furthermore, the reduced species may prove to be a valuable feedstock for other processes. If the incident light utilized is solar then this process also potentially represents energy routes which combine renewable energy with CO2 reduction. == Thermodynamics == Thermodynamic potentials for the reduction of CO2 to various products is given in the following table versus NHE at pH = 7. Single electron reduction of CO2 to CO2●− radical occurs at E° = −1.90 V versus NHE at pH = 7 in an aqueous solution at 25 °C under 1 atm gas pressure. The reason behind the high negative thermodynamically unfavorable single electron reduction potential of CO2 is the


id: pidgeon-process-20260505-0
file: data/en.wikipedia.org/wiki/Pidgeon_process-0.md
category: reference
title: Pidgeon process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pidgeon_process
date_saved: 2026-05-05T10:49:53.068885+00:00
instance: kb-cron
parent: pidgeon-process-20260505-0
summary:
The Pidgeon process is a practical method for smelting magnesium. The most common method involves the raw material, dolomite, being fed into an externally heated reduction tank and then thermally reduced to metallic magnesium using 75% ferrosilicon as a reducing agent in a vacuum. Overall the processes in magnesium smelting via the Pidgeon process involve dolomite calcination, grinding and pelleting, and vacuum thermal reduction. Besides the Pidgeon process, electrolysis of magnesium chloride for commercial production of magnesium is also used, especially for magnesite ores, which at one point in time accounted for 75% of the world's magnesium production. By 2000, it took between 17 and 20 kilowatt-hours per kilogram of magnesium produced by the Pidgeon process. The Pidgeon processes in Canada in the year 2000 all used sulfur hexafluoride (SF6) to cover the reaction so as not to introduce stray oxygen to it. Research to replace SF6 with boron trifluoride was underway in 2000. By 2011, magnesium production had departed under the Kyoto Protocol from Canada. Wu, Han and Liu claimed that "China is the world's largest producer of primary magnesium and has a magnesium smelting industry that is mainly based on the Pidgeon process" in an era in which


id: plasma-electrolytic-oxidation-20260505-0
file: data/en.wikipedia.org/wiki/Plasma_electrolytic_oxidation-0.md
category: reference
title: Plasma electrolytic oxidation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Plasma_electrolytic_oxidation
date_saved: 2026-05-05T10:49:54.290784+00:00
instance: kb-cron
parent: plasma-electrolytic-oxidation-20260505-0
summary:
Plasma electrolytic oxidation (PEO), also known as electrolytic plasma oxidation (EPO) or microarc oxidation (MAO), is an electrochemical surface treatment process for generating oxide coatings on metals. It is similar to anodizing, but it employs higher potentials, so that discharges occur and the resulting plasma modifies the structure of the oxide layer. This process can be used to grow thick (tens or hundreds of micrometers), largely crystalline, oxide coatings on metals such as aluminium, magnesium and titanium. Because they can present high hardness and a continuous barrier, these coatings can offer protection against wear, corrosion or heat as well as electrical insulation. The coating is a chemical conversion of the substrate metal into its oxide, and grows both inwards and outwards from the original metal surface. Because it grows inward into the substrate, it has excellent adhesion to the substrate metal. A wide range of substrate alloys can be coated, including all wrought aluminum alloys and most cast alloys, although high levels of silicon can reduce coating quality. The coating morphology and composition resulting from plasma electrolytic oxidation is largely dependent on the PEO parameters, including voltage, current density, and the electrolytic solution employed. == Process == Metals such as


id: plasma-polymerization-20260505-0
file: data/en.wikipedia.org/wiki/Plasma_polymerization-0.md
category: reference
title: Plasma polymerization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Plasma_polymerization
date_saved: 2026-05-05T10:49:55.489163+00:00
instance: kb-cron
parent: plasma-polymerization-20260505-0
summary:
Plasma polymerization (or glow discharge polymerization) uses plasma sources to generate a gas discharge that provides energy to activate or fragment gaseous or liquid monomer, often containing a vinyl group, in order to initiate polymerization. Polymers formed from this technique are generally highly branched and highly cross-linked, and adhere to solid surfaces well. The biggest advantage to this process is that polymers can be directly attached to a desired surface while the chains are growing, which reduces steps necessary for other coating processes such as grafting. This is very useful for pinhole-free coatings of 100 picometers to 1-micrometer thickness with solvent insoluble polymers. == Introduction == In as early as the 1870s "polymers" formed by this process were known, but these polymers were initially thought of as undesirable byproducts associated with electric discharge, with little attention being given to their properties. It was not until the 1960s that the properties of these polymers were found to be useful. It was found that flawless thin polymeric coatings could be formed on metals, although for very thin films (<10 nm) this has recently been shown to be an oversimplification. By selecting the monomer type and the energy density per monomer, known as


id: plasma-polymerization-20260505-1
file: data/en.wikipedia.org/wiki/Plasma_polymerization-1.md
category: reference
title: Plasma polymerization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Plasma_polymerization
date_saved: 2026-05-05T10:49:55.489163+00:00
instance: kb-cron
parent: plasma-polymerization-20260505-0
summary:
=== Kinetics === The kinetic rate of these reactions depends mostly on the monomer gas, which must be either gaseous or vaporized. However, other parameters are also important as well, such as power, pressure, flow rate, frequency, electrode gap, and reactor configuration. Low flow rates usually only depend on the number of reactive species present for polymerization, whereas high flow rates depend on the amount of time that is spent in the reactor. Therefore, the maximum rate of polymerization is somewhere in the middle. The fastest reactions tend to be in the order of triple-bonded > double-bonded > single bonded molecules, and also lower molecular weight molecules are faster than higher ones. So acetylene is faster than ethylene, and ethylene is faster than propene, etc. The molecular weight factor in polymer deposition is dependent on the monomer flow rate, in which a higher molecular weight monomer typically near 200 g/mol needs a much higher flow rate of 15×104 g/cm2, whereas lower molecular weights around 50 g/mol require a flow rate of only 5×104 g/cm2. A heavy monomer, therefore, needs a faster flow, and would likely lead to increased pressures, decreasing polymerization rates. Increased pressure tends to decrease polymerization rates reducing


id: plasma-polymerization-20260505-2
file: data/en.wikipedia.org/wiki/Plasma_polymerization-2.md
category: reference
title: Plasma polymerization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Plasma_polymerization
date_saved: 2026-05-05T10:49:55.489163+00:00
instance: kb-cron
parent: plasma-polymerization-20260505-0
summary:
Polymerization is likely to take place through either ionic and/or radical processes which are initiated by plasma formed from the glow discharge. The classic view presented by Yasuda based upon thermal initiation of Parylene polymerization is that there are many propagating species present at any given time as shown in Figure 3. This figure shows two different pathways by which the polymerization may take place. The first pathway is a monofunctionalization process, which bears resemblance to a standard free radical polymerization mechanism (M•)- although with the caveat that the reactive species may be ionic and not necessarily radical. The second pathway refers to a difunctional mechanism, which for example may contain a cationic and a radical propagating center on the same monomer (•M•). A consequence is that 'polymer' can grow in multiple directions by multiple pathways off one species, such as a surface or other monomer. This possibility let Yasuda to term the mechanism as a very rapid step-growth polymerization. In the diagram, Mx refers to the original monomer molecule or any of many dissociation products such as chlorine, fluorine and hydrogen. The M• species refers to those that are activated and capable of participating in reactions to form new


id: plasma-polymerization-20260505-3
file: data/en.wikipedia.org/wiki/Plasma_polymerization-3.md
category: reference
title: Plasma polymerization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Plasma_polymerization
date_saved: 2026-05-05T10:49:55.489163+00:00
instance: kb-cron
parent: plasma-polymerization-20260505-0
summary:
The most significant difference between conventional polymers and plasma polymers is that plasma polymers do not contain regular repeating units. Due to the number of different propagating species present at any one time as discussed above, the resultant polymer chains are highly branched and are randomly terminated with a high degree of cross-linking. An example of a proposed structure for plasma polymerized ethylene demonstrating a large extend of cross-linking and branching is shown in Figure 4. All plasma polymers contain free radicals as well. The amount of free radicals present varies between polymers and is dependent on the chemical structure of the monomer. Because the formation of the trapped free radicals is tied to the growth mechanism of the plasma polymers, the overall properties of the polymers directly correlate to the number of free radicals. Plasma polymers also contain internal stress. If a thick layer (e.g. 1 µm) of a plasma polymer is deposited on a glass slide, the plasma polymer will buckle and frequently crack. The curling is attributed to an internal stress formed in the plasma polymer during the polymer deposition. The degree of curling is dependent on the monomer as well as the conditions of the plasma


id: plasma-polymerization-20260505-4
file: data/en.wikipedia.org/wiki/Plasma_polymerization-4.md
category: reference
title: Plasma polymerization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Plasma_polymerization
date_saved: 2026-05-05T10:49:55.489163+00:00
instance: kb-cron
parent: plasma-polymerization-20260505-0
summary:
== Applications == The advantages offered by plasma polymerization have resulted in substantial research on the applications of these polymers. The vastly different chemical and mechanical properties offered by polymers formed with plasma polymerization means they can be applied to countless different systems. Applications ranging from adhesion, composite materials, protective coatings, printing, membranes, biomedical applications, water purification, and so on have all been studied. Of particular interest since the 1980s has been the deposition of functionalized plasma polymer films. For example, functionalized films are used as a means of improving biocompatibility for biological implants6 and for producing super-hydrophobic coatings. They have also been extensively employed in biomaterials for cell attachment, protein binding, and anti-fouling surfaces. Through the use of low-power and pressure plasma, high functional retention can be achieved which has led to substantial improvements in the biocompatibility of some products, a simple example being the development of extended-wear contact lenses. Due to these successes, the huge potential of functional plasma polymers is slowly being realized by workers in previously unrelated fields such as water treatment and wound management. Emerging technologies such as nanopatterning, 3D scaffolds, micro-channel coating, and microencapsulation are now also utilizing functionalized plasma polymers, areas for which


id: post-combustion-capture-20260505-0
file: data/en.wikipedia.org/wiki/Post-combustion_capture-0.md
category: reference
title: Post-combustion capture
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Post-combustion_capture
date_saved: 2026-05-05T10:49:56.679002+00:00
instance: kb-cron
parent: post-combustion-capture-20260505-0
summary:
Post-combustion capture refers to the removal of carbon dioxide (CO2) from a power station flue gas prior to its compression, transportation and storage in suitable geological formations, as part of carbon capture and storage. A number of different techniques are applicable, almost all of which are adaptations of acid gas removal processes used in the chemical and petrochemical industries. Many of these techniques existed before World War II and, consequently, post-combustion capture is the most developed of the various carbon-capture methodologies. Post-combustion capture plant should aim to maximise the capture of CO2 emissions from combustion plant and delivery it to secure sequestration in geological strata. Typically, a plant will aim to achieve a CO2 capture rate of >95%. To meet the required specification, the following should be monitored: CO2 mass balance CO2 in fuel combusted Total CO2 capture level (as a percentage) CO2 released to the environment CO2 quality CO2 can be transported either as gas phase at about 35 barg or as dense phase at 100 barg. The CO2 stream should meet or exceed gas quality standards. CO2 absorbents include primary amines which require more heat for regeneration than secondary amines However, secondary amines may form nitrosamines with Nitrogen


id: powder-coating-on-glass-20260505-0
file: data/en.wikipedia.org/wiki/Powder_coating_on_glass-0.md
category: reference
title: Powder coating on glass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Powder_coating_on_glass
date_saved: 2026-05-05T10:49:57.832376+00:00
instance: kb-cron
parent: powder-coating-on-glass-20260505-0
summary:
Powder coating on glass is a specialized procedure related to traditional powder coating, which is the technique of applying electrostatically charged, dry powdered particles of pigment and resin to a solid item's surface. It requires its own unique process, however, because glass is a poor electrical conductor in comparison to metal, the traditional powder coating substrate. == Markets for glass applications == Powder coating on glass is used in industries such as cosmetics, fragrances, wine and spirits, where the contents inside of the glass containers require protection from ultraviolet (UV) rays, particularly UVA electromagnetic radiation, which is capable of penetrating glass. When applied with a dual-coat method, powder coating techniques on glass provide an opaque shield against the light's effects. == Cleaning preparation == Powder coating on glass requires specialized equipment. The biggest challenge is getting the powder to adhere to the glass surface since there is no natural electrostatic attraction like there is with different metals. A clean glass subsurface that will not interfere with the process is essential before beginning the powder coating procedure. Washing to remove oil, dirt and grease can be accomplished with solvents, wipes or a traditional wash system. Proper temperature control is critical from


id: process-20260505-0
file: data/en.wikipedia.org/wiki/Process-0.md
category: reference
title: Process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Process
date_saved: 2026-05-05T10:49:58.976748+00:00
instance: kb-cron
parent: process-20260505-0
summary:
A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: == Business and management == Business process, activities that produce a specific service or product for customers Business process modeling, activity of representing processes of an enterprise in order to deliver improvements Manufacturing process management, a collection of technologies and methods used to define how products are to be manufactured. Process architecture, structural design of processes, applies to fields such as computers, business processes, logistics, project management Process area, related processes within an area which together satisfies an important goal for improvements within that area Process costing, a cost allocation procedure of managerial accounting Process management (project management), a systematic series of activities directed towards planning, monitoring the performance and causing an end result in engineering activities, business process, manufacturing processes or project management Process-based management, is a management approach that views a business as a collection of processes == Law == Due process, the concept that governments must respect the rule of law Legal process, the proceedings and records of a legal case Service of process, the procedure of giving


id: process-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Process_chemistry-0.md
category: reference
title: Process chemistry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Process_chemistry
date_saved: 2026-05-05T10:50:00.140905+00:00
instance: kb-cron
parent: process-chemistry-20260505-0
summary:
Process chemistry is the arm of pharmaceutical chemistry concerned with the development and optimization of a synthetic scheme and pilot plant procedure to manufacture compounds for the drug development phase. Process chemistry is distinguished from medicinal chemistry, which is the arm of pharmaceutical chemistry tasked with designing and synthesizing molecules on small scale in the early drug discovery phase. Medicinal chemists are largely concerned with synthesizing a large number of compounds as quickly as possible from easily tunable chemical building blocks (usually for SAR studies). In general, the repertoire of reactions utilized in discovery chemistry is somewhat narrow (for example, the Buchwald-Hartwig amination, Suzuki coupling, and reductive amination are commonplace reactions). In contrast, process chemists are tasked with identifying a chemical process that is safe, cost and labor efficient, “green,” and reproducible, among other considerations. Oftentimes, in searching for the shortest, most efficient synthetic route, process chemists must devise creative synthetic solutions that eliminate costly functional group manipulations and oxidation/reduction steps. This article focuses exclusively on the chemical and manufacturing processes associated with the production of small molecule drugs. Biological medical products (more commonly called “biologics”) represent a growing proportion of approved therapies. Additionally, the many complex factors associated with


id: process-chemistry-20260505-1
file: data/en.wikipedia.org/wiki/Process_chemistry-1.md
category: reference
title: Process chemistry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Process_chemistry
date_saved: 2026-05-05T10:50:00.140905+00:00
instance: kb-cron
parent: process-chemistry-20260505-0
summary:
There are several strategies that are employed in the design of a process route to ensure the adequate overall yield of the pharmaceutical product. The first is the concept of convergent synthesis. Assuming a very good to excellent yield in each synthetic step, the overall yield of a multistep reaction can be maximized by combining several key intermediates at a late stage that are prepared independently from each other. Another strategy to maximize isolated yield (as well as time efficiency) is the concept of telescoping synthesis (also called one-pot synthesis). This approach describes the process of eliminating workup and purification steps from a reaction sequence, typically by simply adding reagents sequentially to a reactor. In this way, unnecessary losses from these steps can be avoided. Finally, to minimize overall cost, synthetic steps involving expensive reagents, solvents, or catalysts should be designed into the process route as late stage as possible, to minimize the amount of reagent used. In a pilot plant or manufacturing plant setting, yield can have a profound effect on the material cost of an API synthesis, so the careful planning of a robust route and the fine-tuning of reaction conditions are crucially important. After a synthetic route


id: process-chemistry-20260505-2
file: data/en.wikipedia.org/wiki/Process_chemistry-2.md
category: reference
title: Process chemistry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Process_chemistry
date_saved: 2026-05-05T10:50:00.140905+00:00
instance: kb-cron
parent: process-chemistry-20260505-0
summary:
For this expression, the terms are inverted to reflect the desirability of shorter cycle times (as opposed to higher yields). The reproducibility of cycle times for critical processes such as reaction, centrifugation, or drying may be critical if these operations are rate-limiting in the manufacturing plant setting. For example, if an isolation step is particularly difficult or slow, it could become the bottleneck for API synthesis, in which case the reproducibility and optimization of that operation become critical. For an API manufacturing process, all PEI metrics (yield and cycle times) should be targeted at 98 to 100 percent. === EcoScale === In 2006, Van Aken, et al. developed a quantitative framework to evaluate the safety and ecological impact of a chemical process, as well as minor weighting of practical and economical considerations. Others have modified this EcoScale by adding, subtracting and adjusting the weighting of various metrics. Among other factors, the EcoScale takes into account the toxicity, flammability, and explosive stability of reagents used, any nonstandard or potentially hazardous reaction conditions (for example, elevated pressure or inert atmosphere), and reaction temperature. Some EcoScale criteria are redundant with previously considered criteria (e.g. E-factor). == Synthetic case studies == === Boehringer Ingelheim


id: process-chemistry-20260505-3
file: data/en.wikipedia.org/wiki/Process_chemistry-3.md
category: reference
title: Process chemistry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Process_chemistry
date_saved: 2026-05-05T10:50:00.140905+00:00
instance: kb-cron
parent: process-chemistry-20260505-0
summary:
=== Biocatalysis and enzymatic engineering === Recently, large pharmaceutical process chemists have relied heavily on the development of enzymatic reactions to produce important chiral building blocks for API synthesis. Many varied classes of naturally occurring enzymes have been co-opted and engineered for process pharmaceutical chemistry applications. The widest range of applications come from ketoreductases and transaminases, but there are isolated examples from hydrolases, aldolases, oxidative enzymes, esterases and dehalogenases, among others. One of the most prominent uses of biocatalysis in process chemistry today is in the synthesis of Januvia®, a DPP-4 inhibitor developed by Merck for the management of type II diabetes. The traditional process synthetic route involved a late-stage enamine formation followed by rhodium-catalyzed asymmetric hydrogenation to afford the API sitagliptin. This process suffered from a number of limitations, including the need to run the reaction under a high-pressure hydrogen environment, the high cost of a transition-metal catalyst, the difficult process of carbon treatment to remove trace amounts of catalyst and insufficient stereoselectivity, requiring a subsequent recrystallization step before final salt formation. Merck's process chemistry department contracted Codexis, a medium-sized biocatalysis firm, to develop a large-scale biocatalytic reductive amination for the final step of its sitagliptin synthesis. Codexis engineered


id: process-engineering-20260505-0
file: data/en.wikipedia.org/wiki/Process_engineering-0.md
category: reference
title: Process engineering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Process_engineering
date_saved: 2026-05-05T10:50:01.343201+00:00
instance: kb-cron
parent: process-engineering-20260505-0
summary:
Process engineering is a field of study focused on the development and optimization of industrial processes. It consists of the understanding and application of the fundamental principles and laws of nature to allow humans to transform raw material and energy into products that are useful to society, at an industrial level. By taking advantage of the driving forces of nature such as pressure, temperature and concentration gradients, as well as the law of conservation of mass, process engineers can develop methods to synthesize and purify large quantities of desired chemical products. Process engineering focuses on the design, operation, control, optimization and intensification of chemical, physical, and biological processes. Their work involves analyzing the chemical makeup of various ingredients and determining how they might react with one another. A process engineer can specialize in a number of areas, including the following: Agriculture processing Food and dairy production Beer and whiskey production Cosmetics production Pharmaceutical production Petrochemical manufacturing Mineral processing Printed circuit board production == Overview == Process engineering involves the utilization of multiple tools and methods. Depending on the exact nature of the system, processes need to be simulated and modeled using mathematics and computer science. Processes where phase change and


id: propane-refrigeration-20260505-0
file: data/en.wikipedia.org/wiki/Propane_refrigeration-0.md
category: reference
title: Propane refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Propane_refrigeration
date_saved: 2026-05-05T10:50:02.529067+00:00
instance: kb-cron
parent: propane-refrigeration-20260505-0
summary:
Propane refrigeration is a type of compression refrigeration. Propane (R-290) has been used successfully in industrial refrigeration for many years, and is emerging as an increasingly viable alternative for homes and businesses. Propane's operating pressures and temperatures are well suited for use in air conditioning equipment, but because of propane’s flammability, great care is required in the manufacture, installation and servicing of equipment that uses it as a refrigerant. Propane that is supplied for general use – such as in barbeques and patio heaters – is not suitable for use in refrigeration systems because it can contain high levels of contaminants, including moisture and unsaturated hydrocarbons. Only propane produced specifically for use in refrigeration systems – with a purity of at least 98.5% and moisture content below 10ppm (by weight) – should be used. With a global warming potential (GWP) of 0.072 and an ozone depletion potential (ODP) of 0, R-290 is of very little threat to the environment. The Environmental Protection Agency (EPA) has listed R-290 as an acceptable refrigerant substitute under its Significant New Alternatives Policy (SNAP), and recently exempted it from the venting prohibition in Section 608 of the Clean Air Act. == References ==


id: pulse-electrolysis-20260505-0
file: data/en.wikipedia.org/wiki/Pulse_electrolysis-0.md
category: reference
title: Pulse electrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pulse_electrolysis
date_saved: 2026-05-05T10:50:04.871665+00:00
instance: kb-cron
parent: pulse-electrolysis-20260505-0
summary:
Pulse electrolysis is an alternate electrolysis method that utilises a pulsed direct current to initiate non-spontaneous chemical reactions. Also known as pulsed direct current (PDC) electrolysis, the increased number of variables that it introduces to the electrolysis method can change the application of the current to the electrodes and the resulting outcome. This varies from direct current (DC) electrolysis, which only allows the variation of one value, the voltage applied. By utilising conventional pulse width modulation (PMW), multiple dependent variables can be altered, including the type of waveform, typically a rectangular pulse wave, the duty cycle, and the frequency. Currently, there has been a focus on theoretical and experimental research into PDC electrolysis in terms of the electrolysis of water to produce hydrogen. Claims have been made that there is a possibility it can result in a higher electrical efficiency in comparison to DC water electrolysis, but past research has shown this is not the case. The varying voltage and current added on top of the DC cause additional energy consumption with no effect on the hydrogen production. Because of the increasing energy consumption, attempts to replicate claimed benefits experimentally have not succeeded, and have found negative effects on the


id: pulse-electrolysis-20260505-1
file: data/en.wikipedia.org/wiki/Pulse_electrolysis-1.md
category: reference
title: Pulse electrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pulse_electrolysis
date_saved: 2026-05-05T10:50:04.871665+00:00
instance: kb-cron
parent: pulse-electrolysis-20260505-0
summary:
=== Use in Magnetolisis === Electrolysers require high currents produced by very low voltages. A homopolar generator has the ability to do this, so in Bockris and Ghoroghchian's original experiment in 1985, they followed Faraday's idea. Using a magnetic field of 0.86T produced by permanent magnets, they placed a stainless-steel disc in between. The disc needed a rotation speed of 2000 rpm to reach the correct electrical potential for electrolysis. The difference between Faraday's original model and Bockris and Ghorogchian's is that their disc will only rotate when it is in contact with an electrolyte. They encountered one large problem, a viscous force created by the electrolyte, that slowed down the motion of the disc. The two ways they could fix this is to rotate the disc and solution together or increase the magnetic field used. The latter being most practicable, the required magnetic field was calculated according to the power consumption rate or producing a cubic meter of hydrogen. It was discovered a magnetic field of 11T was needed for effective electrolysis, more than 16 times greater than what was originally used. Since superconducting magnets would be required, and they can become too expensive to justify their use, ruling


id: pulse-electrolysis-20260505-2
file: data/en.wikipedia.org/wiki/Pulse_electrolysis-2.md
category: reference
title: Pulse electrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pulse_electrolysis
date_saved: 2026-05-05T10:50:04.871665+00:00
instance: kb-cron
parent: pulse-electrolysis-20260505-0
summary:
== Claimed advantages == In theoretical electrolysis of water, a voltage of only 1.23 V is required to split water into hydrogen and oxygen. The formation of an EDL increases this to its thermo-neutral voltage of 1.45 V. It is claimed that minimising the EDL formed during pulse electrolysis is advantageous, as it can reduce the thermo-neutral voltage and the energy input required, increasing energy efficiency. However, this claim follows from a misconseption regarding energy consumption in the system when varying current and voltage waveforms are applied. The hydrogen production rate in the process is determined by the mean of the current waveform, according to the Faraday's law of electrolysis, but the mean of the voltage waveform is not sufficient to evaluate the rate of energy consumption. Instead, the mean of the product of instantaneous current and voltage should be assessed, revealing increased energy consumption due to the alternating current and voltage waveforms, in comparison to DC water electrolysis with an equal hydrogen production rate. == Disadvantages == Whilst the method of PDC electrolysis has been claimed by Ghoroghichian and Bockris in 1952 and 1985 to work extremely well in theory, it is difficult to replicate with consistently positive results


id: pyrolysis-20260505-0
file: data/en.wikipedia.org/wiki/Pyrolysis-0.md
category: reference
title: Pyrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pyrolysis
date_saved: 2026-05-05T10:50:06.171621+00:00
instance: kb-cron
parent: pyrolysis-20260505-0
summary:
Pyrolysis (; from Ancient Greek πῦρ (pûr) 'fire' and λύσις (lúsis) 'separation') is a process involving the separation of covalent bonds in organic matter by thermal decomposition within an inert environment without oxygen. == Applications == Pyrolysis is most commonly used in the treatment of organic materials. It is one of the processes involved in the charring of wood. In general, pyrolysis of organic substances produces volatile products and leaves char, a carbon-rich solid residue. Extreme pyrolysis, which leaves mostly carbon as the residue, is called carbonization. Pyrolysis is considered one of the steps in the processes of gasification or combustion. Compared to syngas, pyrolysis gas has a high percentage of heavy tar fractions, which condense at relatively high temperatures, preventing its direct use in gas burners and internal combustion engines. The process is used heavily in the chemical industry, for example, to produce ethylene, many forms of carbon, and other chemicals from petroleum, coal, and even wood, or to produce coke from coal. It is used also in the conversion of natural gas (primarily methane) into hydrogen gas and solid carbon char, recently introduced on an industrial scale. Aspirational applications of pyrolysis would convert biomass into syngas and biochar,


id: pyrolysis-20260505-1
file: data/en.wikipedia.org/wiki/Pyrolysis-1.md
category: reference
title: Pyrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pyrolysis
date_saved: 2026-05-05T10:50:06.171621+00:00
instance: kb-cron
parent: pyrolysis-20260505-0
summary:
Below about 100 °C, volatiles, including some water, evaporate. Heat-sensitive substances, such as vitamin C and proteins, may partially change or decompose already at this stage. At about 100 °C or slightly higher, any remaining water that is merely absorbed in the material is driven off. This process consumes a lot of energy, so the temperature may stop rising until all water has evaporated. Water trapped in crystal structure of hydrates may come off at somewhat higher temperatures. Some solid substances, like fats, waxes, and sugars, may melt and separate. Between 100 and 500 °C, many common organic molecules break down. Most sugars start decomposing at 160–180 °C. Cellulose, a major component of wood, paper, & and cotton fabrics, decomposes at about 350 °C. Lignin, another major wood component, starts decomposing at about 350 °C, but continues releasing volatile products up to 500 °C. The decomposition products usually include water, carbon monoxide CO and/or carbon dioxide CO2, as well as a large number of organic compounds. Gases and volatile products leave the sample, and some of them may condense again as smoke. Generally, this process also absorbs energy. Some volatiles may ignite and burn, creating a visible flame. The non-volatile


id: pyrolysis-20260505-2
file: data/en.wikipedia.org/wiki/Pyrolysis-2.md
category: reference
title: Pyrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pyrolysis
date_saved: 2026-05-05T10:50:06.171621+00:00
instance: kb-cron
parent: pyrolysis-20260505-0
summary:
The coke-making or "coking" process consists of heating the material in "coking ovens" to very high temperatures (up to 900 °C or 1,700 °F) so that the molecules are broken down into lighter volatile substances, which leave the vessel, and a porous but hard residue that is mostly carbon and inorganic ash. The amount of volatiles varies with the source material, but is typically 25–30% of it by weight. High temperature pyrolysis is used on an industrial scale to convert coal into coke. This is useful in metallurgy, where the higher temperatures are necessary for many processes, such as steelmaking. Volatile by-products of this process are also often useful, including benzene and pyridine. Coke can also be produced from the solid residue left from petroleum refining. The original vascular structure of the wood and the pores created by escaping gases combine to produce a light and porous material. By starting with a dense wood-like material, such as nutshells or peach stones, one obtains a form of charcoal with particularly fine pores (and hence a much larger pore surface area), called activated carbon, which is used as an adsorbent for a wide range of chemical substances. Biochar is the residue of


id: pyrolysis-20260505-3
file: data/en.wikipedia.org/wiki/Pyrolysis-3.md
category: reference
title: Pyrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pyrolysis
date_saved: 2026-05-05T10:50:06.171621+00:00
instance: kb-cron
parent: pyrolysis-20260505-0
summary:
Methane pyrolysis is an industrial process for "turquoise" hydrogen production from methane by removing solid carbon from natural gas. This one-step process produces hydrogen in high volume at low cost (less than steam reforming with carbon sequestration). No greenhouse gas is released. No deep well injection of carbon dioxide is needed. Only water is released when hydrogen is used as the fuel for fuel-cell electric heavy truck transportation, gas turbine electric power generation, and hydrogen for industrial processes including producing ammonia fertilizer and cement. Methane pyrolysis is the process operating around 1065 °C for producing hydrogen from natural gas that allows removal of carbon easily (solid carbon is a byproduct of the process). The industrial quality solid carbon can then be sold or landfilled and is not released into the atmosphere, avoiding emission of greenhouse gas (GHG) or ground water pollution from a landfill. In 2015, a company called Monolith Materials built a pilot plant in Redwood City, CA to study scaling Methane Pyrolysis using renewable power in the process. A successful pilot project then led to a larger commercial-scale demonstration plant in Hallam, Nebraska in 2016. As of 2020, this plant is operational and can produce around 14 metric


id: pyrolysis-20260505-4
file: data/en.wikipedia.org/wiki/Pyrolysis-4.md
category: reference
title: Pyrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pyrolysis
date_saved: 2026-05-05T10:50:06.171621+00:00
instance: kb-cron
parent: pyrolysis-20260505-0
summary:
Pyrolysis can also be used to treat municipal solid waste and plastic waste. The main advantage is the reduction in volume of the waste. In principle, pyrolysis will regenerate the monomers (precursors) to the polymers that are treated, but in practice the process is neither a clean nor an economically competitive source of monomers. In tire waste management, tire pyrolysis is a well-developed technology. Other products from car tire pyrolysis include steel wires, carbon black and bitumen. The area faces legislative, economic, and marketing obstacles. Oil derived from tire rubber pyrolysis has a high sulfur content, which gives it high potential as a pollutant; consequently it should be desulfurized. Alkaline pyrolysis of sewage sludge at low temperature of 500 °C can enhance H2 production with in-situ carbon capture. The use of NaOH (sodium hydroxide) has the potential to produce H2-rich gas that can be used for fuels cells directly. In early November 2021, the U.S. State of Georgia announced a joint effort with Igneo Technologies to build an $85 million large electronics recycling plant in the Port of Savannah. The project will focus on lower-value, plastics-heavy devices in the waste stream using multiple shredders and furnaces using pyrolysis technology. Waste


id: pyrolysis-20260505-5
file: data/en.wikipedia.org/wiki/Pyrolysis-5.md
category: reference
title: Pyrolysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pyrolysis
date_saved: 2026-05-05T10:50:06.171621+00:00
instance: kb-cron
parent: pyrolysis-20260505-0
summary:
The one-stepwise pyrolysis experiment showed different results for the CO2 and N2 environments. During this process the evolution of 5 different notable gases were observed. Hydrogen, Methane, Ethane, Carbon Dioxide, and Ethylene all are produced when the thermolytic rate of TLW began to be retarded at greater than or equal to 500 °C. Thermolytic rate begins at the same temperatures for both the CO2 and N2 environment but there is higher concentration of the production of Hydrogen, Ethane, Ethylene, and Methane in the N2 environment than that in the CO2 environment. The concentration of CO in the CO2 environment is significantly greater as temperatures increase past 600 °C and this is due to CO2 being liberated from CaCO3 in TLW. This significant increase in CO concentration is why there is lower concentrations of other gases produced in the CO2 environment due to a dilution effect. Since pyrolysis is the re-distribution of carbons in carbon substrates into three pyrogenic products. The CO2 environment is going to be more effective because the CO2 reduction into CO allows for the oxidation of pyrolysates to form CO. In conclusion the CO2 environment allows a higher yield of gases than oil and biochar. When the


id: pyroprocessing-20260505-0
file: data/en.wikipedia.org/wiki/Pyroprocessing-0.md
category: reference
title: Pyroprocessing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pyroprocessing
date_saved: 2026-05-05T10:50:07.358316+00:00
instance: kb-cron
parent: pyroprocessing-20260505-0
summary:
Pyroprocessing (from Greek Πυρος = fire) is a process in which materials are subjected to high temperatures (typically over 800 °C) in order to bring about a chemical or physical change. Pyroprocessing includes such terms as ore-roasting, calcination and sintering. Equipment for pyroprocessing includes kilns, electric arc furnaces and reverberatory furnaces. Cement manufacturing is a very common example of pyroprocessing. The raw material mix (raw meal) is fed to a kiln where pyroprocessing takes place. As with most industries, pyroprocessing is the most energy-intensive part of the industrial process. == Recycling used nuclear fuel through pyroprocessing == Argonne National Laboratory pioneered the development of pyrochemical processing, or pyroprocessing, a high-temperature method of recycling reactor waste into fuel, demonstrating it paired with the EBR-II and then proposed commercializing it in the Integral Fast Reactor. The latter was cancelled by the Clinton Administration in 1994. In 2016, Argonne National Laboratory researchers are developing and refining several pyroprocessing technologies for both light water and fast reactors, with most based on electrorefining rather than conventional wet-chemical/PUREX, to improve the technologies’ commercial viability by increasing their process efficiency and scalability. Animations of the processing technology are also available. Pyroprocessing of nuclear fuel rods, as an


id: quenching-scrubber-20260505-0
file: data/en.wikipedia.org/wiki/Quenching_(scrubber)-0.md
category: reference
title: Quenching (scrubber)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Quenching_(scrubber)
date_saved: 2026-05-05T10:50:08.543119+00:00
instance: kb-cron
parent: quenching-scrubber-20260505-0
summary:
Quenching, in the context of pollution scrubbers, is the cooling of hot exhaust gas by water sprays before it enters the scrubber proper. Hot gases (those above ambient temperature) are often cooled to near the saturation level. If not cooled, the hot gas stream can evaporate a large portion of the scrubbing liquor, adversely affecting collection efficiency and damaging scrubber internal parts. If the gases entering the scrubber are too hot, some liquid droplets may evaporate before they have a chance to contact pollutants in the exhaust stream, and others may evaporate after contact, causing captured particles to become reentrained. In some cases, quenching can actually save money. Cooling the gases reduces the temperature and, therefore, the volume of gases, permitting the use of less expensive construction materials and a smaller scrubber vessel and fan. == Design == A quenching system can be as simple as spraying liquid into the duct just preceding the main scrubbing vessel, or it can be a separate chamber (or tower) with its own spray system identical to a spray tower. Quenchers are designed using the same principles as scrubbers. Increasing the gas-liquid contact in them increases their operational efficiency. == Sizing == Small liquid


id: raschig-hydroxylamine-process-20260505-0
file: data/en.wikipedia.org/wiki/Raschig_hydroxylamine_process-0.md
category: reference
title: Raschig hydroxylamine process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Raschig_hydroxylamine_process
date_saved: 2026-05-05T10:50:09.715458+00:00
instance: kb-cron
parent: raschig-hydroxylamine-process-20260505-0
summary:
The Raschig process for the production of hydroxylamine is one of three chemical processes developed by German chemist Friedrich Raschig. The main step in this process, patented by Raschig in 1887, is the reduction of nitrite with bisulfite towards hydroxylamine disulfonate, which is hydrolysed to hydroxylammonium sulfate. Most of the hydroxylamine produced is used in the manufacture of caprolactam, the precursor to the polymer Nylon 6. The commercially used Raschig process consists of the following steps: ammonium carbonate solution is prepared by reacting ammonia, carbon dioxide and water an alkaline solution of ammonium nitrite is formed by reacting ammonium carbonate solution with nitrogen oxides ammonium nitrite is converted to hydroxylamine disulfonate with bisulfite (obtained by blowing sulfur dioxide through the carbonate solution) hydroxylamine disulfonate is hydrolysed to hydroxylammonium sulfate == References ==


id: raschig-hooker-process-20260505-0
file: data/en.wikipedia.org/wiki/Raschig–Hooker_process-0.md
category: reference
title: Raschig–Hooker process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Raschig–Hooker_process
date_saved: 2026-05-05T10:50:10.903492+00:00
instance: kb-cron
parent: raschig-hooker-process-20260505-0
summary:
The Raschig–Hooker process is a chemical process for the production of chlorobenzene and phenol from benzene. The main steps in this process are the production of chlorobenzene from benzene, hydrochloric acid and oxygen, and the subsequent hydrolysis of chlorobenzene to phenol. The first step uses either a copper or iron chloride catalyst and exposes the materials to air at 200–250 °C. In the second step, the resulting chlorobenzene is introduced to steam at 450 °C over a silicon catalyst that hydrolyses the chlorobenzene, giving phenol and hydrogen chloride that can then be recycled back to the first step. Due to the two step nature, the Raschig–Hooker process can be used to produce either chlorobenzene or phenol. == Comparison to other processes == The Raschig–Hooker route to phenol from benzene is comparable to the Dow and Bayer process, which also convert benzene into phenol. The recycling of the hydrogen chloride made the Raschig–Hooker process preferable to the Dow and Bayer process, which requires its sodium chloride product to be converted into chlorine and sodium hydroxide. The reaction, however, requires very high temperatures in a very acidic environment with hydrogen chloride vapor and therefore the industrial setting must use highly corrosion resistant


id: reactive-flash-volatilization-20260505-0
file: data/en.wikipedia.org/wiki/Reactive_flash_volatilization-0.md
category: reference
title: Reactive flash volatilization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reactive_flash_volatilization
date_saved: 2026-05-05T10:50:12.048679+00:00
instance: kb-cron
parent: reactive-flash-volatilization-20260505-0
summary:
Reactive flash volatilization (RFV) is a chemical process that rapidly converts nonvolatile solids and liquids to volatile compounds by thermal decomposition for integration with catalytic chemistries. == Chemistry == The utilization of heavy fossil fuels or biomass rich in carbohydrates, (C6H10O5)n, for fuels or chemicals requires an initial thermochemical process called pyrolysis which fractures large polymers to mixtures of small volatile organic compounds (VOCs). A specific method of pyrolysis of biomass, termed "fast pyrolysis," converts particles of biomass to about 10% carbon-rich solid called char, about 15% gases such as carbon dioxide, and about 70% a mixture of organic compounds commonly referred to as "bio-oil" at 500 °C in 1–2 seconds. Pyrolysis: Biomass + Heat → 0.70VOCs + 0.10Char + 0.15Gases The volatile organics can be collected as a brown, highly acidic liquid for further thermochemical conversion by traditional processes such as steam reforming, gasification, catalytic partial oxidation, catalytic cracking, combustion, or hydrotreating. [2] Catalytic steam reforming: VOCs + H2O + Heat + Catalyst → H2 + CO + Catalyst Catalytic partial oxidation: VOCs + O2 + Catalyst → H2 + CO + Heat + Catalyst Catalytic combustion: VOCs + O2 + Catalyst → CO2 + H2O + Heat +


id: recrystallization-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Recrystallization_(chemistry)-0.md
category: reference
title: Recrystallization (chemistry)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Recrystallization_(chemistry)
date_saved: 2026-05-05T10:50:13.204998+00:00
instance: kb-cron
parent: recrystallization-chemistry-20260505-0
summary:
Recrystallization is a broad class of chemical purification techniques characterized by the dissolution of an impure sample in a solvent or solvent mixture, followed by some change in conditions that encourages the formation of pure isolate as solid crystals. Recrystallization as a purification technique is driven by spontaneous processes of self-assembly that leverage the highly ordered (i.e. low-entropy) and periodic characteristics of a crystal's molecular structure to produce purification. == Basic principles == The driving force of this purification emerges from the difference in molecular interactions between the isolate and the impurities: if a molecule of the desired isolate interacts with any isolate crystal present, it is likely the molecule deposits on the crystal's ordered surface and contributes to the crystal's growth; if a molecule of the impurity interacts with any isolate crystal present, it is unlikely to deposit on the crystal's ordered surface, and thus stays dissolved in the solvent. Initial crystals of isolate form by processes of stochastic nucleation and grow to macroscopic sizes when isolate molecules in solution deposit on them. The simplest example of recrystallization is by temperature manipulation of a solution where the isolate compound has an endothermic dissolution (ΔH > 0) and a solubility


id: rectisol-20260505-0
file: data/en.wikipedia.org/wiki/Rectisol-0.md
category: reference
title: Rectisol
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rectisol
date_saved: 2026-05-05T10:50:14.390457+00:00
instance: kb-cron
parent: rectisol-20260505-0
summary:
Rectisol is the trade name for an acid gas removal process that uses methanol as a solvent to separate acid gases such as hydrogen sulfide and carbon dioxide from valuable feed gas streams. By doing so, the feed gas is made more suitable for combustion and/or further processing. Rectisol is used most often to treat synthesis gas (primarily hydrogen and carbon monoxide) produced by gasification of coal or heavy hydrocarbons, as the methanol solvent is well able to remove trace contaminants such as ammonia, mercury, and hydrogen cyanide usually found in these gases. As an acid gas and large component of valuable feed gas streams, CO2 is separated during the methanol solvent regeneration. == Process description == In the Rectisol process (licensed by both Linde AG and Air Liquide), cold methanol at approximately –40 °F (–40 °C) dissolves (absorbs) the acid gases from the feed gas at relatively high pressure, usually 400 to 1000 psia (2.76 to 6.89 MPa). The rich solvent containing the acid gases is then let down in pressure to release and recover the acid gases. The Rectisol process can operate selectively to recover hydrogen sulfide and carbon dioxide as separate streams, so that the hydrogen sulfide


id: redistribution-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Redistribution_(chemistry)-0.md
category: reference
title: Redistribution (chemistry)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Redistribution_(chemistry)
date_saved: 2026-05-05T10:50:15.546243+00:00
instance: kb-cron
parent: redistribution-chemistry-20260505-0
summary:
In chemistry, redistribution usually refers to the exchange of anionic ligands bonded to metal and metalloid centers. The conversion does not involve redox, in contrast to disproportionation reactions. Some useful redistribution reactions are conducted at higher temperatures; upon cooling the mixture, the product mixture is kinetically frozen and the individual products can be separated. In cases where redistribution is rapid at mild temperatures, the reaction is less useful synthetically but still important mechanistically. == Examples == Redistribution reactions are exhibited by methylboranes. Thus monomethyldiborane rapidly converts at room temperature to diborane and trimethylborane: 6 MeB2H5 → 5 B2H6 + 2 Me3B Useful redistribution reactions are found in organoaluminium, organoboron, and organosilicon chemistry. BCl3 + 2 B(C2H5)3 → 3 BCl(C2H5)2 In another example, tetramethylsilane is an undesirable product of the industrially important direct process, but it can be converted (recycled) into more useful products by redistribution with silicon tetrachloride: SiMe4 + SiCl4 → 2 SiMe2Cl2 In organotin chemistry, the mixed alkyl tin chlorides are produced by redistribution, a reaction called the Kocheshkov comproportionation: 3 SnBu4 + SnCl4 → 4 SnBu3Cl Many metal halides undergo redistribution reactions, usually to afford nearly statistical mixtures of products. For example, titanium tetrachloride and titanium tetrabromide


id: refinery-20260505-0
file: data/en.wikipedia.org/wiki/Refinery-0.md
category: reference
title: Refinery
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refinery
date_saved: 2026-05-05T10:50:16.668262+00:00
instance: kb-cron
parent: refinery-20260505-0
summary:
A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value. == Types of refineries == Different types of refineries are as follows: Petroleum oil refinery, which converts crude oil into high-octane motor spirit (gasoline/petrol), diesel oil, liquefied petroleum gases (LPG), kerosene, heating fuel oils, hexane, lubricating oils, bitumen, and petroleum coke Edible oil refinery which converts cooking oil into a product that is uniform in taste, smell and appearance, and stability Natural gas processing plant, which purifies and converts raw natural gas into residential, commercial and industrial fuel gas, and also recovers natural gas liquids (NGL) such as ethane, propane, butanes and pentanes Sugar refinery, which converts sugar cane and sugar beets into crystallized sugar and sugar syrups Salt refinery, which cleans common salt (NaCl), produced by the solar evaporation of sea water, followed by washing and re-crystallization Metal refineries refining metals such as alumina, copper, gold, lead, nickel, silver, uranium, zinc, magnesium and cobalt Iron refining, a stage of refining pig iron (typically grey cast iron to white cast iron), before fining, which converts pig iron into bar iron or


id: reflux-20260505-0
file: data/en.wikipedia.org/wiki/Reflux-0.md
category: reference
title: Reflux
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reflux
date_saved: 2026-05-05T10:50:17.858866+00:00
instance: kb-cron
parent: reflux-20260505-0
summary:
Reflux is a technique involving the condensation of vapors and the return of this condensate to the system from which it originated. It is used in industrial and laboratory distillations. It is also used in chemistry to supply energy to reactions over a long period of time. == Reflux in industrial distillation == The term reflux is very widely used in industries that utilize large-scale distillation columns and fractionators such as petroleum refineries, petrochemical and chemical plants, and natural gas processing plants. In that context, reflux refers to the portion of the overhead liquid product from a distillation column or fractionator that is returned to the upper part of the column as shown in the schematic diagram of a typical industrial distillation column. Inside the column, the downflowing reflux liquid provides cooling and condensation of the upflowing vapors thereby increasing the efficiency of the distillation column. The more reflux provided for a given number of theoretical plates, the better is the column's separation of lower boiling materials from higher boiling materials. Conversely, for a given desired separation, the more reflux is provided, the fewer theoretical plates are required. == Reflux in chemical reactions == A mixture of reactants and solvent


id: refrigeration-20260505-0
file: data/en.wikipedia.org/wiki/Refrigeration-0.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
Refrigeration is any of various types of cooling of a space, substance, or system to lower or maintain its temperature below the ambient one (while the removed heat is rejected at a higher temperature). Refrigeration is an artificial, or human-made, cooling method. Refrigeration refers to the process by which energy, in the form of heat, is removed from a low-temperature medium and transferred to a high-temperature medium. This work of energy transfer is traditionally driven by mechanical means (whether ice or electromechanical machines), but it can also be driven by heat, magnetism, electricity, laser, or other means. Refrigeration has many applications, including household refrigerators, industrial freezers, cryogenics, and air conditioning. Heat pumps may use the heat output of the refrigeration process, and also may be designed to be reversible, but are otherwise similar to air conditioning units. Refrigeration has had a large impact on industry, lifestyle, agriculture, and settlement patterns. The idea of preserving food dates back to human prehistory, but for thousands of years humans were limited regarding the means of doing so. They used curing via salting and drying, and they made use of natural coolness in caves, root cellars, and winter weather, but other means of cooling


id: refrigeration-20260505-1
file: data/en.wikipedia.org/wiki/Refrigeration-1.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
Before 1830, few Americans used ice to refrigerate foods due to a lack of ice-storehouses and iceboxes. As these two things became more widely available, individuals used axes and saws to harvest ice for their storehouses. This method proved to be difficult, dangerous, and certainly did not resemble anything that could be duplicated on a commercial scale. Despite the difficulties of harvesting ice, Frederic Tudor thought that he could capitalize on this new commodity by harvesting ice in New England and shipping it to the Caribbean islands as well as the southern states. In the beginning, Tudor lost thousands of dollars, but eventually turned a profit as he constructed icehouses in Charleston, Virginia and in the Cuban port town of Havana. These icehouses as well as better insulated ships helped reduce ice wastage from 66% to 8%. This efficiency gain influenced Tudor to expand his ice market to other towns with icehouses such as New Orleans and Savannah. This ice market further expanded as harvesting ice became faster and cheaper after one of Tudor's suppliers, Nathaniel Wyeth, invented a horse-drawn ice cutter in 1825. This invention as well as Tudor's success inspired others to get involved in the ice trade


id: refrigeration-20260505-2
file: data/en.wikipedia.org/wiki/Refrigeration-2.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
The first gas absorption refrigeration system using gaseous ammonia dissolved in water (referred to as "aqua ammonia") was developed by Ferdinand Carré in 1859 and patented in 1860. Carl von Linde, an engineer specializing in steam locomotives and professor of engineering at the Technological University of Munich, began researching refrigeration in the 1860s and 1870s in response to demand from brewers for a technology that would allow year-round, large-scale production of lager; he patented an improved method of liquefying gases in 1876. His new process made possible using gases such as ammonia, sulfur dioxide (SO2) and methyl chloride (CH3Cl) as refrigerants and they were widely used for that purpose until the late 1920s. Thaddeus Lowe, a balloonist, held several patents on ice-making machines. His "Compression Ice Machine" would revolutionize the cold-storage industry. In 1869, he and other investors purchased an old steamship onto which they loaded one of Lowe's refrigeration units and began shipping fresh fruit from New York to the Gulf Coast area, and fresh meat from Galveston, Texas back to New York, but because of Lowe's lack of knowledge about shipping, the business was a costly failure. === Commercial use === In 1842, John Gorrie created a system


id: refrigeration-20260505-3
file: data/en.wikipedia.org/wiki/Refrigeration-3.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
The new refrigerating technology first met with widespread industrial use as a means to freeze meat supplies for transport by sea in reefer ships from the British Dominions and other countries to the British Isles. Although not actually the first to achieve successful transportation of frozen goods overseas (the Strathleven had arrived at the London docks on 2 February 1880 with a cargo of frozen beef, mutton and butter from Sydney and Melbourne), the breakthrough is often attributed to William Soltau Davidson, an entrepreneur who had emigrated to New Zealand. Davidson thought that Britain's rising population and meat demand could mitigate the slump in world wool markets that was heavily affecting New Zealand. After extensive research, he commissioned the Dunedin to be refitted with a compression refrigeration unit for meat shipment in 1881. On February 15, 1882, the Dunedin sailed for London with what was to be the first commercially successful refrigerated shipping voyage, and the foundation of the refrigerated meat industry. The Times commented "Today we have to record such a triumph over physical difficulties, as would have been incredible, even unimaginable, a very few days ago ...". The Marlborough — sister ship to the Dunedin — was immediately


id: refrigeration-20260505-4
file: data/en.wikipedia.org/wiki/Refrigeration-4.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
In the last century, refrigeration allowed new settlement patterns to emerge. This new technology has allowed for new areas to be settled that are not on a natural channel of transport such as a river, valley trail or harbor that may have otherwise not been settled. Refrigeration has given opportunities to early settlers to expand westward and into rural areas that were unpopulated. These new settlers with rich and untapped soil saw opportunity to profit by sending raw goods to the eastern cities and states. In the 20th century, refrigeration has made "Galactic Cities" such as Dallas, Phoenix, and Los Angeles possible. === Refrigerated rail cars === The refrigerated rail car (refrigerated van or refrigerator car), along with the dense railroad network, became an exceedingly important link between the marketplace and the farm allowing for a national opportunity rather than a just a regional one. Before the invention of the refrigerated rail car, it was impossible to ship perishable food products long distances. The beef packing industry made the first demand push for refrigeration cars. The railroad companies were slow to adopt this new invention because of their heavy investments in cattle cars, stockyards, and feedlots. Refrigeration cars were also


id: refrigeration-20260505-5
file: data/en.wikipedia.org/wiki/Refrigeration-5.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
=== Rise of the galactic city === "Edge city" was a term coined by Joel Garreau, whereas the term "galactic city" was coined by Lewis Mumford. These terms refer to a concentration of business, shopping, and entertainment outside a traditional downtown or central business district in what had previously been a residential or rural area. There were several factors contributing to the growth of these cities such as Los Angeles, Las Vegas, Houston, and Phoenix. The factors that contributed to these large cities include reliable automobiles, highway systems, refrigeration, and agricultural production increases. Large cities such as the ones mentioned above have not been uncommon in history, but what separates these cities from the rest are that these cities are not along some natural channel of transport, or at some crossroad of two or more channels such as a trail, harbor, mountain, river, or valley. These large cities have been developed in areas that only a few hundred years ago would have been uninhabitable. Without a cost efficient way of cooling air and transporting water and food from great distances, these large cities would have never developed. The rapid growth of these cities was influenced by refrigeration and an agricultural


id: refrigeration-20260505-6
file: data/en.wikipedia.org/wiki/Refrigeration-6.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
=== Farm use === In order to reduce humidity levels and spoiling due to bacterial growth, refrigeration is used for meat, produce, and dairy processing in farming today. Refrigeration systems are used the heaviest in the warmer months for farming produce, which must be cooled as soon as possible in order to meet quality standards and increase the shelf life. Meanwhile, dairy farms refrigerate milk year round to avoid spoiling. == Effects on lifestyle and diet == In the late 19th Century and into the very early 20th Century, except for staple foods (sugar, rice, and beans) that needed no refrigeration, the available foods were affected heavily by the seasons and what could be grown locally. Refrigeration has removed these limitations. Refrigeration played a large part in the feasibility and then popularity of the modern supermarket. Fruits and vegetables out of season, or grown in distant locations, are now available at relatively low prices. Refrigerators have led to a huge increase in meat and dairy products as a portion of overall supermarket sales. As well as changing the goods purchased at the market, the ability to store these foods for extended periods of time has led to an increase in


id: refrigeration-20260505-7
file: data/en.wikipedia.org/wiki/Refrigeration-7.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
This consists of a refrigeration cycle, where heat is removed from a low-temperature space or source and rejected to a high-temperature sink with the help of external work, and its inverse, the thermodynamic power cycle. In the power cycle, heat is supplied from a high-temperature source to the engine, part of the heat being used to produce work and the rest being rejected to a low-temperature sink. This satisfies the second law of thermodynamics. A refrigeration cycle describes the changes that take place in the refrigerant as it alternately absorbs and rejects heat as it circulates through a refrigerator. It is also applied to heating, ventilation, and air conditioning HVACR work, when describing the "process" of refrigerant flow through an HVACR unit, whether it is a packaged or split system. Heat naturally flows from hot to cold. Work is applied to cool a living space or storage volume by pumping heat from a lower temperature heat source into a higher temperature heat sink. Insulation is used to reduce the work and energy needed to achieve and maintain a lower temperature in the cooled space. The operating principle of the refrigeration cycle was described mathematically by Sadi Carnot in 1824 as


id: refrigeration-20260505-8
file: data/en.wikipedia.org/wiki/Refrigeration-8.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
When the working fluid is a gas that is compressed and expanded but does not change phase, the refrigeration cycle is called a gas cycle. Air is most often this working fluid. As there is no condensation and evaporation intended in a gas cycle, components corresponding to the condenser and evaporator in a vapor compression cycle are the hot and cold gas-to-gas heat exchangers in gas cycles. The gas cycle is less efficient than the vapor compression cycle because the gas cycle works on the reverse Brayton cycle instead of the reverse Rankine cycle. As such, the working fluid does not receive and reject heat at constant temperature. In the gas cycle, the refrigeration effect is equal to the product of the specific heat of the gas and the rise in temperature of the gas in the low temperature side. Therefore, for the same cooling load, a gas refrigeration cycle needs a large mass flow rate and is bulky. Because of their lower efficiency and larger bulk, air cycle coolers are not often used nowadays in terrestrial cooling devices. However, the air cycle machine is very common on gas turbine-powered jet aircraft as cooling and ventilation units, because compressed air


id: refrigeration-20260505-9
file: data/en.wikipedia.org/wiki/Refrigeration-9.md
category: reference
title: Refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refrigeration
date_saved: 2026-05-05T10:50:19.104070+00:00
instance: kb-cron
parent: refrigeration-20260505-0
summary:
=== Fridge Gate === The Fridge Gate method is a theoretical application of using a single logic gate to drive a refrigerator in the most energy efficient way possible without violating the laws of thermodynamics. It operates on the fact that there are two energy states in which a particle can exist: the ground state and the excited state. The excited state carries a little more energy than the ground state, small enough so that the transition occurs with high probability. There are three components or particle types associated with the fridge gate. The first is on the interior of the refrigerator, the second on the outside and the third is connected to a power supply which heats up every so often that it can reach the E state and replenish the source. In the cooling step on the inside of the refrigerator, the g state particle absorbs energy from ambient particles, cooling them, and itself jumping to the e state. In the second step, on the outside of the refrigerator where the particles are also at an e state, the particle falls to the g state, releasing energy and heating the outside particles. In the third and final step,


id: rescue-fusion-hybridization-20260505-0
file: data/en.wikipedia.org/wiki/Rescue_fusion_hybridization-0.md
category: reference
title: Rescue fusion hybridization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rescue_fusion_hybridization
date_saved: 2026-05-05T10:50:20.250019+00:00
instance: kb-cron
parent: rescue-fusion-hybridization-20260505-0
summary:
Rescue fusion hybridization is a process used to manufacture some therapeutic cancer vaccines in which individual tumor cells obtained through biopsy are fused with an antibody-secreting cell to form a heterohybridoma. This cell then secretes the unique idiotype, or immunoglobulin antigen characteristic of the individual tumor, which is purified for use as the vaccine. It is used to produce the BiovaxID vaccine for follicular lymphoma. == References ==


id: saponification-20260505-0
file: data/en.wikipedia.org/wiki/Saponification-0.md
category: reference
title: Saponification
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Saponification
date_saved: 2026-05-05T10:50:21.416329+00:00
instance: kb-cron
parent: saponification-20260505-0
summary:
Saponification is a process of cleaving esters into carboxylate salts and alcohols by the action of aqueous alkali. Typically aqueous sodium hydroxide solutions are used. It is an important type of alkaline hydrolysis. When the carboxylate is a long chain, its salt is called a soap. The saponification of ethyl acetate gives sodium acetate and ethanol: C2H5O2CCH3 + NaOH → C2H5OH + NaO2CCH3 == Saponification of fats == Vegetable oils and animal fats are the traditional materials that are saponified. These greasy materials, triesters called triglycerides, are usually mixtures derived from diverse fatty acids. In the traditional saponification, the triglyceride is treated with lye, which cleaves the ester bonds, releasing fatty acid salts (soaps) and glycerol. In one simplified version, the saponification of stearin gives sodium stearate. C3H5(O2C(CH2)16CH3)3 + 3 NaOH → C3H5(OH)3 + 3 NaO2C(CH2)16CH3 This process is the main industrial method for producing glycerol (C3H5(OH)3). Some soap-makers leave the glycerol in the soap. Others precipitate the soap by salting it out with sodium chloride. Fat in a corpse converts into adipocere, often called "grave wax". This process is more common where the amount of fatty tissue is high and the agents of decomposition are absent or only minutely


id: selective-catalytic-reduction-20260505-0
file: data/en.wikipedia.org/wiki/Selective_catalytic_reduction-0.md
category: reference
title: Selective catalytic reduction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Selective_catalytic_reduction
date_saved: 2026-05-05T10:50:22.632604+00:00
instance: kb-cron
parent: selective-catalytic-reduction-20260505-0
summary:
Selective catalytic reduction (SCR) means converting nitrogen oxides, also referred to as NOx with the aid of a catalyst into diatomic nitrogen (N2), and water (H2O). A reductant, typically anhydrous ammonia (NH3), aqueous ammonia (NH4OH), or a urea (CO(NH2)2) solution, is added to a stream of flue or exhaust gas and is reacted onto a catalyst. As the reaction drives toward completion, nitrogen (N2), and carbon dioxide (CO2), in the case of urea use, are produced. Selective catalytic reduction of NOx using ammonia as the reducing agent was patented in the United States by the Engelhard Corporation in 1957. Development of SCR technology continued in Japan and the US in the early 1960s with research focusing on less expensive and more durable catalyst agents. The first large-scale SCR was installed by the IHI Corporation in 1978. Commercial selective catalytic reduction systems are typically found on large utility boilers, industrial boilers, and municipal solid waste boilers and have been shown to lower NOx emissions by 70-95%. Applications include diesel engines, such as those found on large ships, diesel locomotives, gas turbines, and automobiles. SCR systems are now the preferred method for meeting Tier 4 Final and EURO 6 diesel emissions standards


id: selective-catalytic-reduction-20260505-1
file: data/en.wikipedia.org/wiki/Selective_catalytic_reduction-1.md
category: reference
title: Selective catalytic reduction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Selective_catalytic_reduction
date_saved: 2026-05-05T10:50:22.632604+00:00
instance: kb-cron
parent: selective-catalytic-reduction-20260505-0
summary:
== Catalysts == SCR catalysts are made from various porous ceramic materials used as a support, such as titanium oxide, and active catalytic components are usually either oxides (of vanadium, molybdenum and tungsten), zeolites, or cerium. Base metal catalysts, such as vanadium and tungsten, lack high thermal durability, but are less expensive and operate very well at the temperature ranges most commonly applied in industrial and utility boiler applications. Thermal durability is particularly important for automotive SCR applications that incorporate the use of a diesel particulate filter with forced regeneration. They also have a high catalysing potential to oxidize SO2 into SO3, which can be extremely damaging due to its acidic properties. Zeolite catalysts have the potential to operate at substantially higher temperature than base metal catalysts; they can withstand prolonged operation at temperatures of 900 K (627 °C) and transient conditions of up to 1120 K (847 °C). Zeolites also have a lower potential for SO2 oxidation and thus decrease the related corrosion risks. Iron- and copper-exchanged zeolite urea SCRs have been developed with approximately equal performance to that of vanadium-urea SCRs if the fraction of the NO2 is 20% to 50% of the total NOx. The two most


id: selective-catalytic-reduction-20260505-2
file: data/en.wikipedia.org/wiki/Selective_catalytic_reduction-2.md
category: reference
title: Selective catalytic reduction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Selective_catalytic_reduction
date_saved: 2026-05-05T10:50:22.632604+00:00
instance: kb-cron
parent: selective-catalytic-reduction-20260505-0
summary:
Temperature is SCR's largest limitation. Engines all have a period during start-up where exhaust temperatures are too low, and the catalyst must be pre-heated for the desired NOx reduction to occur when an engine is first started, especially in cold climates. == Power plants == In power stations, the same basic technology is employed for removal of NOx from the flue gas of boilers used in power generation and industry. In general, the SCR unit is located between the furnace economizer and the air heater, and the ammonia is injected into the catalyst chamber through an ammonia injection grid. As in other SCR applications, the temperature of operation is critical. Ammonia slip (unreacted ammonia) is also an issue with SCR technology used in power plants. A significant operational difficulty in coal-fired boilers is the binding of the catalyst by fly ash from the fuel combustion. This requires the usage of sootblowers, ultrasonic horns, and careful design of the ductwork and catalyst materials to avoid plugging by the fly ash. SCR catalysts have a typical operational lifetime of about 16,000 – 40,000 hours (1.8 – 4.5 years) in coal-fired power plants, depending on the flue gas composition, and up to 80,000


id: selexol-20260505-0
file: data/en.wikipedia.org/wiki/Selexol-0.md
category: reference
title: Selexol
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Selexol
date_saved: 2026-05-05T10:50:23.837567+00:00
instance: kb-cron
parent: selexol-20260505-0
summary:
Selexol is the trade name for an acid gas removal solvent that can separate acid gases such as hydrogen sulfide and carbon dioxide from feed gas streams such as synthesis gas produced by gasification of coal, coke, or heavy hydrocarbon oils. By doing so, the feed gas is made more suitable (less sour) for combustion and/or further processing. It is made up of dimethyl ethers of polyethylene glycol. == Process description == In the Selexol process (now licensed by UOP LLC), the Selexol solvent dissolves (absorbs) the acid gases from the feed gas at relatively high pressure, usually 300 to 2000 psia (2.07 to 13.8 MPa). The rich solvent containing the acid gases is then let down in pressure and/or steam stripped to release and recover the acid gases. The Selexol process can operate selectively to recover hydrogen sulfide and carbon dioxide as separate streams, so that the hydrogen sulfide can be sent to either a Claus unit for conversion to elemental sulfur or to a wet sulfuric acid process unit for conversion to sulfuric acid while, at the same time, the carbon dioxide can be sequestered or used for enhanced oil recovery. The Selexol process is similar to the


id: shell-higher-olefin-process-20260505-0
file: data/en.wikipedia.org/wiki/Shell_higher_olefin_process-0.md
category: reference
title: Shell higher olefin process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Shell_higher_olefin_process
date_saved: 2026-05-05T10:50:24.984629+00:00
instance: kb-cron
parent: shell-higher-olefin-process-20260505-0
summary:
The Shell higher olefin process (SHOP) is a chemical process for the production of linear alpha olefins via ethylene oligomerization and olefin metathesis invented and exploited by Shell plc. The olefin products are converted to fatty aldehydes and then to fatty alcohols, which are precursors to plasticizers and detergents. The annual global production of olefins through this method is over one million tonnes. == History == The process was discovered by chemists at Shell Development Emeryville in 1968. At the time ecological considerations demanded the replacement of branched fatty alcohols used widely in detergents by linear fatty alcohols because the biodegradation of the branched compounds was slow, causing foaming of surface water. At the same time new gas oil crackers were being commissioned and ethylene supply was outpacing demand. The process was commercialized in 1977 by Shell plc and following an expansion of the Geismar, Louisiana (USA) plant in 2002 global annual production capacity was 1.2 million tons. == Process == Ethylene reacts by the catalyst to give longer chains. Unlike the Ziegler–Natta process, which aims to produce very long polymers, the oligomer stops growing after addition of 1–10 repeating units of ethylene. The fraction containing C12 to C18 olefins


id: sherardising-20260505-0
file: data/en.wikipedia.org/wiki/Sherardising-0.md
category: reference
title: Sherardising
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sherardising
date_saved: 2026-05-05T10:50:26.176076+00:00
instance: kb-cron
parent: sherardising-20260505-0
summary:
Sherardising or Zinc thermal diffusion is a process of galvanization of ferrous metal surfaces, also called vapour galvanising and dry galvanizing. The process is named after British metallurgist Sherard Osborn Cowper-Coles (son of naval inventor Cowper Phipps Coles) who invented and patented the method c. 1900. This process involves heating the steel parts up to 500 °C in a closed rotating drum that contains metallic zinc dust and possibly an inert filler, such as sand. At temperatures above 300 °C, zinc evaporates and diffuses into the steel substrate forming diffusion bonded Zn-Fe-phases. Sherardising is ideal for small parts and parts that require coating of inner surfaces, such as batches of small items. Part size is limited by drum size. It is reported that pipes up to 6 m in length for the oil industry are sherardised. If the metal surface is free of scale or oxides, no pretreatment is needed. The process is hydrogen-free, hence hydrogen embrittlement is prevented. == Application == During and shortly after World War I, German 5 pfennig and 10 pfennig coins were sherardised. == Standards == ISO 17668:2016 (replaced BS EN 13811:2003): Sherardizing. Zinc diffusion coatings on ferrous products. Specification ISO 14713-3:2017: Zinc coatings. Guidelines


id: shukhov-cracking-process-20260505-0
file: data/en.wikipedia.org/wiki/Shukhov_cracking_process-0.md
category: reference
title: Shukhov cracking process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Shukhov_cracking_process
date_saved: 2026-05-05T10:50:27.352891+00:00
instance: kb-cron
parent: shukhov-cracking-process-20260505-0
summary:
The Shukhov cracking process is a thermal cracking process invented by Vladimir Shukhov and Sergei Gavrilov. == Origins == Shukhov designed and built the first thermal cracking device for the petrochemical industry. His patent (Shukhov cracking process – patent of Russian Empire No. 12926 from November 27, 1891) on cracking was used to invalidate Standard Oil's patents (Burton process – Patent of United States No. 1,049,667 on January 7, 1913) on oil refineries. == Present == In 1937 the Shukhov cracking process was superseded by catalytic cracking. It is still in use today to produce diesel. == See also == Cracking (chemistry) Timeline of historic inventions Burton process == References == Information on cracking in oil refining Biography of Vladimir Shukhov "Vladimir G. Suchov 1853-1939. Die Kunst der sparsamen Konstruktion.", Rainer Graefe und andere, 192 S., Deutsche Verlags-Anstalt, Stuttgart, 1990, ISBN 3-421-02984-9.


id: silvering-20260505-0
file: data/en.wikipedia.org/wiki/Silvering-0.md
category: reference
title: Silvering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Silvering
date_saved: 2026-05-05T10:50:28.502299+00:00
instance: kb-cron
parent: silvering-20260505-0
summary:
Silvering is the chemical process of coating a non-conductive substrate such as glass with a reflective substance, to produce a mirror. While the metal is often silver, the term is used for the application of any reflective metal. == Process == Most common household mirrors are "back-silvered" or "second-surface", meaning that the light reaches the reflective layer after passing through the glass. A protective layer of paint is usually applied to protect the back side of the reflective surface. This arrangement protects the fragile reflective layer from corrosion, scratches, and other damage. However, the glass layer may absorb some of the light and cause distortions and optical aberrations due to refraction at the front surface, and multiple additional reflections on it, giving rise to "ghost images" (although some optical mirrors such as Mangin mirrors take advantage of it). Therefore, precision optical mirrors normally are "front-silvered" or "first-surface", meaning that the reflective layer is on the surface towards the incoming light. The substrate normally provides only physical support, and need not be transparent. A hard, protective, transparent overcoat may be applied to prevent oxidation of the reflective layer and scratching of the metal. Front-coated mirrors achieve reflectivities of 90–95% when new.


id: silylation-20260505-0
file: data/en.wikipedia.org/wiki/Silylation-0.md
category: reference
title: Silylation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Silylation
date_saved: 2026-05-05T10:50:29.675687+00:00
instance: kb-cron
parent: silylation-20260505-0
summary:
Silylation is the introduction of one or more (usually) substituted silyl groups (R3Si) to a molecule. Silylations are core methods for production of organosilicon chemistry. Silanization, while similar to silylation, usually refers to attachment of silyl groups to solids. Silyl groups are commonly used for: alcohol protection, enolate trapping, gas chromatography, electron-impact mass spectrometry (EI-MS), and coordinating with metal complexes. == Protection chemistry == === Protection === Silylation is often used to protect alcohols, as well as amines, carboxylic acids, and terminal alkynes. The products after silylation, namely silyl ethers and silyl amines, are resilient toward basic conditions. Protection is typically done by reacting the functional group with a silyl halide by an SN2 reaction mechanism, typically in the presence of base. The protection mechanism begins with the base deprotonating the alcohol group. Next, the deprotonated alcohol group attacks the silyl atom of the silyl halide compound. The halide acts as a leaving group and ends up in solution. A workup step follows to remove any excess base within the solution. The overall reaction scheme is as follows: ROH + NEt3 → RO− + H−NEt+3 RO− + Cl−SiMe3 → RO−SiMe3 + Cl− Other silylating agents include bis(trimethylsilyl)acetamide (BSA). The reaction


id: single-layer-etching-20260505-0
file: data/en.wikipedia.org/wiki/Single_layer_etching-0.md
category: reference
title: Single layer etching
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single_layer_etching
date_saved: 2026-05-05T10:50:30.904982+00:00
instance: kb-cron
parent: single-layer-etching-20260505-0
summary:
Single layer etching is a chemical processing technique that removes material one atomic or molecular layer at a time. Manufacturers apply the technique in semiconductor fabrication for precise control over device features as sizes shrink below 10 nm. Atomic layer etching (ALE) targets individual atomic layers. Molecular layer etching (MLE) focuses on molecular layers, often in organic or hybrid inorganic-organic films. These self-limiting methods provide nanoscale precision and smooth surfaces. Single layer etching removes material one layer at a time at the atomic or molecular scale. Manufacturers use the technique in semiconductor fabrication for precise control over device features. Atomic layer etching (ALE) targets atomic layers. Molecular layer etching (MLE) focuses on molecular layers, often in organic or hybrid films. == Process == ALE employs sequential, self-limiting reactions. The cycle consists of surface modification followed by removal. Modification exposes the surface to chemicals or plasma that react with the top atomic layer to form a reactive species. Removal uses low-energy ions or other agents to desorb the modified layer. The process repeats, with etch depth determined by cycle count. For silicon, chlorine gas or plasma chlorinates the surface to form a silicon chloride layer roughly 0.5 nm thick. Argon ions


id: smart-cosubstrate-20260505-0
file: data/en.wikipedia.org/wiki/Smart_cosubstrate-0.md
category: reference
title: Smart cosubstrate
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Smart_cosubstrate
date_saved: 2026-05-05T10:50:32.090432+00:00
instance: kb-cron
parent: smart-cosubstrate-20260505-0
summary:
A smart cosubstrate is a type of cosubstrate used for cofactor regeneration to yield greater productivity and lower environmental impact (E-factor). A good example of a smart cosubstrate is a lactonizable diol. In redox biocatalysis, the nicotinamide cofactor (NAD(P)H or NAD(P)+) can act as an electron donor or acceptor by releasing or accepting a hydride. The cofactor must be used in the reaction either in stoichiometric amounts leading to inhibition and economic issues, or in catalytic amounts coupled with an in situ regeneration system. A common approach catalytic amounts is excess use of sacrificial organic molecules such as isopropanol or ethanol. This approach, however, leads to stoichiometric amounts of waste. The use of 1,4-butanediol as a smart cosubstrate for cofactor regeneration was the next step towards more sustainable redox biocatalysis (Scheme 1). The formation of a thermodynamically stable gamma-butyrolactone as a co-product drives the reaction to completion while yielding higher reaction rates. The use of 1,4-butanediol as an intelligent cosubstrate has also been validated in non-aqueous media using a commercial ADH. == Double-smart cosubstrate == Biocatalytic cascade reactions currently fall into four different categories: Linear, which is biocatalytic Orthogonal Parallel Cyclic However, only two types of redox-neutral cascades have been


id: snow-bleaching-20260505-0
file: data/en.wikipedia.org/wiki/Snow_bleaching-0.md
category: reference
title: Snow bleaching
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Snow_bleaching
date_saved: 2026-05-05T10:50:33.256815+00:00
instance: kb-cron
parent: snow-bleaching-20260505-0
summary:
Snow bleaching is a technique used in traditional Japanese textile industry to bleach the fabric using the ozone evaporating from snow. This technique is used to bleach Echigo-jofu, a type of kimono. This method is based on the fact that ozone is released when snow evaporates due to sunlight. == References ==


id: snox-process-20260505-0
file: data/en.wikipedia.org/wiki/SNOX_process-0.md
category: reference
title: SNOX process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/SNOX_process
date_saved: 2026-05-05T10:50:34.420169+00:00
instance: kb-cron
parent: snox-process-20260505-0
summary:
The SNOX process is a process which removes sulfur dioxide, nitrogen oxides and particulates from flue gases. The sulfur is recovered as concentrated sulfuric acid and the nitrogen oxides are reduced to free nitrogen. The process is based on the well-known wet sulfuric acid process (WSA), a process for recovering sulfur from various process gases in the form of commercial quality sulfuric acid (H2SO4). The SNOX process is based on catalytic reactions and does not consume water or absorbents. Neither does it produce any waste, except for the separated dust. In addition the process can handle other sulfurous waste streams. This is highly interesting in refineries, where e.g. hydrogen sulfide (H2S) gas, sour water stripper gas and Claus tail gas can be led to the SNOX plant, and thereby investment in other waste gas handling facilities can be saved. == Process == The SNOX process includes the following steps: Dust removal Catalytic reduction of NOx by adding NH3 to the gas upstream of the SCR DeNOx reactor Catalytic oxidation of SO2 to SO3 in the oxidation reactor Cooling of the gas to about 100 °C whereby the H2SO4 condenses and can be withdrawn as concentrated sulfuric acid == Applications ==


id: soda-pulping-20260505-0
file: data/en.wikipedia.org/wiki/Soda_pulping-0.md
category: reference
title: Soda pulping
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Soda_pulping
date_saved: 2026-05-05T10:50:35.610909+00:00
instance: kb-cron
parent: soda-pulping-20260505-0
summary:
Soda pulping is a chemical process for making wood pulp with sodium hydroxide as the cooking chemical. In the Soda-AQ process, anthraquinone (AQ) may be used as a pulping additive to decrease the carbohydrate degradation. The soda process gives pulp with lower tear strength than other chemical pulping processes (sulfite process and kraft process), but has still limited use for easily pulped materials like straw and some hardwoods. == History == A precursor to the soda pulping process was the paper making process developed by Matthias Koops in 1801 which involved washing wood shavings in limewater, adding soda crystals and then boiling the mixture. Soda pulping was one of the first chemical pulping methods and was invented in 1851 by Burgess (United States) and Watts (England). In France in 1852 Coupier and Mellier patented a soda process based on an 1851 invention the patent of which preceded that of Watt and Burgess, which was filed in 1854. The first mill was started in 1866 in the USA. In 1865 they patented a method for recovery of the cooking liquors by incineration of the spent liquor. Many of the early soda mills converted to kraft mills once it was discovered. ==


id: solar-air-conditioning-20260505-0
file: data/en.wikipedia.org/wiki/Solar_air_conditioning-0.md
category: reference
title: Solar air conditioning
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_air_conditioning
date_saved: 2026-05-05T10:50:36.769032+00:00
instance: kb-cron
parent: solar-air-conditioning-20260505-0
summary:
Solar air conditioning, or "solar-powered air conditioning", refers to any air conditioning (cooling) system that uses solar power. This can be done through passive solar design, solar thermal energy conversion, and photovoltaic conversion (sunlight to electricity). The U.S. Energy Independence and Security Act of 2007 created 2008 through 2012 funding for a new solar air conditioning research and development program, which should develop and demonstrate multiple new technology innovations and mass production economies of scale. == History == In the late 19th century, the most common fluid for absorption cooling was a solution of ammonia and water. Today, the combination of lithium bromide and water is also in common use. One end of the system of expansion/condensation pipes is heated, and the other end gets cold enough to make ice. Originally, natural gas was used as a heat source in the late 19th century. Today, propane is used in recreational vehicle absorption chiller refrigerators. Hot water solar thermal energy collectors can also be used as the modern "free energy" heat source. A National Aeronautics and Space Administration (NASA) sponsored report in 1976 surveyed solar energy system applications of air conditioning. Techniques discussed included both solar powered (absorption cycle and heat


id: solar-air-conditioning-20260505-1
file: data/en.wikipedia.org/wiki/Solar_air_conditioning-1.md
category: reference
title: Solar air conditioning
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_air_conditioning
date_saved: 2026-05-05T10:50:36.769032+00:00
instance: kb-cron
parent: solar-air-conditioning-20260505-0
summary:
Photovoltaics can provide either indirect solar air conditioning power or, now, directly power to air conditioners. Indirect photovoltaic power for air conditioners consists of whole-house or whole-building solar which, traditionally for most users, has also meant net metering to the grid. Solar in this case is inverted to alternating current (AC) to run the appliances in the house or building, including the air conditioner(s). The advantage of this is the air conditioners don’t need any special electronics to accommodate solar, so it’s a simple implementation. The disadvantage is that these air conditioners usually have a SEER value of 14 or less, and the supplied solar has some loss from the power conversion of DC (direct current) solar to AC even before it reaches the air conditioners. Another disadvantage is that these air conditioners cannot run when the grid is down, since, in effect, the net-metered home or building is a node on the grid, and utilities need to prevent backfeeding power into a dead grid when the grid’s down. And, now, air conditioners, like many home appliances (e.g., TVs, computers) are beginning to run on DC power. So, whole-building solar for such units needs to be inverted to alternating current,


id: solar-air-conditioning-20260505-2
file: data/en.wikipedia.org/wiki/Solar_air_conditioning-2.md
category: reference
title: Solar air conditioning
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_air_conditioning
date_saved: 2026-05-05T10:50:36.769032+00:00
instance: kb-cron
parent: solar-air-conditioning-20260505-0
summary:
== Geothermal cooling == Earth sheltering or earth cooling tubes can take advantage of the ambient temperature of the earth to reduce or eliminate conventional air conditioning requirements. In many climates where the majority of humans live, they can greatly reduce the buildup of undesirable summer heat, and also help remove heat from the interior of the building. They increase construction cost, but reduce or eliminate the cost of conventional air conditioning equipment. Earth cooling tubes are not cost effective in hot humid tropical environments where the ambient Earth temperature approaches human temperature comfort zone. A solar chimney or photovoltaic-powered fan can be used to exhaust undesired heat and draw in cooler, dehumidified air that has passed by ambient Earth temperature surfaces. Control of humidity and condensation are important design issues. A geothermal heat pump uses ambient earth temperature to improve SEER for heat and cooling. A deep well recirculates water to extract ambient earth temperature, typically at 8 litres (2 US gal) of water per metric ton per minute. These "open loop" systems were the most common in early systems, however water quality could cause damage to the coils in the heat pump and shorten the life of the


id: solar-air-conditioning-20260505-3
file: data/en.wikipedia.org/wiki/Solar_air_conditioning-3.md
category: reference
title: Solar air conditioning
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solar_air_conditioning
date_saved: 2026-05-05T10:50:36.769032+00:00
instance: kb-cron
parent: solar-air-conditioning-20260505-0
summary:
Ammonia Lithium Bromide Lithium Chloride Silica Gel Zeolite An alternative to water-based systems is to use methanol with activated carbon. Active solar cooling uses solar thermal collectors to provide solar energy to thermally driven chillers (usually adsorption or absorption chillers). Solar energy heats a fluid that provides heat to the generator of an absorption chiller and is recirculated back to the collectors. The heat provided to the generator drives a cooling cycle that produces chilled water. The chilled water produced is used for large commercial and industrial cooling. Solar thermal energy can be used to efficiently cool in the summer, and also heat domestic hot water and buildings in the winter. Single, double or triple iterative absorption cooling cycles are used in different solar-thermal-cooling system designs. The more cycles, the more efficient they are. Absorption chillers operate with less noise and vibration than compressor-based chillers, but their capital costs are relatively high. Efficient absorption chillers nominally require water of at least 190 °F (88 °C). Common, inexpensive flat-plate solar thermal collectors only produce about 160 °F (71 °C) water. High temperature flat plate, concentrating (CSP) or evacuated tube collectors are needed to produce the higher temperature transfer fluids required. In


id: solvated-metal-atom-dispersion-20260505-0
file: data/en.wikipedia.org/wiki/Solvated_metal_atom_dispersion-0.md
category: reference
title: Solvated metal atom dispersion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solvated_metal_atom_dispersion
date_saved: 2026-05-05T10:50:38.083935+00:00
instance: kb-cron
parent: solvated-metal-atom-dispersion-20260505-0
summary:
Solvated metal atom dispersion is a method of producing highly reactive solvated nanoparticles. Samples of a metal (or ceramic) are heated to evaporate free atoms (or species), as in PVD evaporation. This vapor is then co-deposited with a suitable organic solvent (e.g. toluene) at very low temperatures (on the order of 70K) to form a solid mixture of the two. This is then warmed towards room temperature, producing solvated metal atoms or (over time) larger clusters. Sometimes, catalyst supports (such as SiO2 or Al2O3) are added to improve nucleation, as the process can more readily take place on surface OH groups. == References ==


id: solvation-20260505-0
file: data/en.wikipedia.org/wiki/Solvation-0.md
category: reference
title: Solvation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solvation
date_saved: 2026-05-05T10:50:39.316005+00:00
instance: kb-cron
parent: solvation-20260505-0
summary:
Solvation is the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the solute, including solubility, reactivity, and color, as well as influencing the properties of the solvent such as its viscosity and density. If the attractive forces between the solvent and solute particles are greater than the attractive forces holding the solute particles together, the solvent particles pull the solute particles apart and surround them. The surrounded solute particles then move away from the solid solute and out into the solution. Ions are surrounded by a concentric shell of solvent. Solvation is the process of reorganizing solvent and solute molecules into solvation complexes and involves bond formation, hydrogen bonding, and van der Waals forces. Solvation of a solute by water is called hydration. Solubility of solid compounds depends on a competition between lattice energy and solvation, including entropy effects related to changes in the solvent structure. == Distinction from solubility == By an IUPAC definition, solvation is an interaction of a solute with the solvent, which leads to stabilization of the solute species in the solution. In the solvated


id: solvation-20260505-1
file: data/en.wikipedia.org/wiki/Solvation-1.md
category: reference
title: Solvation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solvation
date_saved: 2026-05-05T10:50:39.316005+00:00
instance: kb-cron
parent: solvation-20260505-0
summary:
The enthalpy of solution is the solution enthalpy minus the enthalpy of the separate systems, whereas the entropy of solution is the corresponding difference in entropy. The solvation energy (change in Gibbs free energy) is the change in enthalpy minus the product of temperature (in Kelvin) multiplied by the change in entropy. Gases have a negative entropy of solution, due to the decrease in gaseous volume as gas dissolves. Since their enthalpy of solution does not decrease too much with temperature, and their entropy of solution is negative and does not vary appreciably with temperature, most gases are less soluble at higher temperatures. Enthalpy of solvation can help explain why solvation occurs with some ionic lattices but not with others. The difference in energy between that which is necessary to release an ion from its lattice and the energy given off when it combines with a solvent molecule is called the enthalpy change of solution. A negative value for the enthalpy change of solution corresponds to an ion that is likely to dissolve, whereas a high positive value means that solvation will not occur. It is possible that an ion will dissolve even if it has a positive enthalpy value.


id: solvay-process-20260505-0
file: data/en.wikipedia.org/wiki/Solvay_process-0.md
category: reference
title: Solvay process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solvay_process
date_saved: 2026-05-05T10:50:40.492402+00:00
instance: kb-cron
parent: solvay-process-20260505-0
summary:
The Solvay process or ammonia–soda process is the major industrial process for the production of sodium carbonate (soda ash, Na2CO3). The ammonia–soda process was developed into its modern form by the Belgian chemist Ernest Solvay during the 1860s. The ingredients for this are readily available and inexpensive: salt brine (from inland sources or from the sea) and limestone (from quarries). The worldwide production of soda ash in 2005 was estimated at 42 million tonnes, which is more than six kilograms (13 lb) per year for each person on Earth. Solvay-based chemical plants now produce roughly three-quarters of this supply, with the remaining being mined from natural deposits. This method superseded the Leblanc process. == History == The name "soda ash" is based on the principal historical method of obtaining alkali, which was by using water to extract it from the ashes of certain plants. Wood fires yielded potash and its predominant ingredient potassium carbonate (K2CO3), whereas the ashes from these special plants yielded "soda ash" and its predominant ingredient sodium carbonate (Na2CO3). The word "soda" (from the Middle Latin) originally referred to certain plants that grow in salt solubles; it was discovered that the ashes of these plants yielded the


id: solvay-process-20260505-1
file: data/en.wikipedia.org/wiki/Solvay_process-1.md
category: reference
title: Solvay process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solvay_process
date_saved: 2026-05-05T10:50:40.492402+00:00
instance: kb-cron
parent: solvay-process-20260505-0
summary:
NaCl + CO 2 + NH 3 + H 2 O ⟶ NaHCO 3 + NH 4 Cl {\displaystyle {\ce {NaCl + CO2 + NH3 + H2O -> NaHCO3 + NH4Cl}}} ---(I) In industrial practice, the reaction is carried out by passing concentrated brine (salt water) through two towers. In the first, ammonia bubbles up through the brine and is absorbed by it. In the second, carbon dioxide bubbles up through the ammoniated brine, and sodium bicarbonate (baking soda) precipitates out of the solution. Note that, in a basic solution, NaHCO3 is less water-soluble than sodium chloride. The ammonia (NH3) buffers the solution at a basic (high) pH; without the ammonia, a hydrochloric acid byproduct would render the solution acidic, and arrest the precipitation. Here, NH3 along with ammoniacal brine acts as a mother liquor. The necessary ammonia "catalyst" for reaction (I) is reclaimed in a later step, and relatively little ammonia is consumed. The carbon dioxide required for reaction (I) is produced by heating ("calcination") of the limestone at 950–1100 °C, and by calcination of the sodium bicarbonate (see below). The calcium carbonate (CaCO3) in the limestone is partially converted to quicklime (calcium oxide (CaO)) and carbon dioxide: CaCO


id: solvay-process-20260505-2
file: data/en.wikipedia.org/wiki/Solvay_process-2.md
category: reference
title: Solvay process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solvay_process
date_saved: 2026-05-05T10:50:40.492402+00:00
instance: kb-cron
parent: solvay-process-20260505-0
summary:
== Carbon sequestration and the Solvay process == Variations in the Solvay process have been proposed for carbon sequestration. One idea is to react carbon dioxide, produced perhaps by the combustion of coal, to form solid carbonates (such as sodium bicarbonate) that could be permanently stored, thus avoiding carbon dioxide emission into the atmosphere. The Solvay process could be modified to give the overall reaction: 2 NaCl + CaCO3 + CO2 + H2O → 2NaHCO3 + CaCl2 Variations in the Solvay process have been proposed to convert carbon dioxide emissions into sodium carbonates, but carbon sequestration by calcium or magnesium carbonates appears more promising. However, the amount of carbon dioxide which can be used for carbon sequestration with calcium or magnesium (when compared to the total amount of carbon dioxide exhausted by mankind) is very low. This is primarily due to the major feasibility difference between capturing carbon dioxide from controlled and concentrated emission sources such as from coal-fired power plants as compared to capturing carbon from non-concentrated small-scale carbon sources such as small fires, vehicle exhaust, human respiration etc. when using such methods. Moreover, variation on the Solvay process will most probably add an additional energy consuming step, which


id: sorption-enhanced-water-gas-shift-20260505-0
file: data/en.wikipedia.org/wiki/Sorption_enhanced_water_gas_shift-0.md
category: reference
title: Sorption enhanced water gas shift
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sorption_enhanced_water_gas_shift
date_saved: 2026-05-05T10:50:41.661583+00:00
instance: kb-cron
parent: sorption-enhanced-water-gas-shift-20260505-0
summary:
Sorption enhanced water gas shift (SEWGS) is a technology that combines a pre-combustion carbon capture process with the water gas shift reaction (WGS) in order to produce a hydrogen rich stream from the syngas fed to the SEWGS reactor. The water gas shift reaction converts the carbon monoxide into carbon dioxide, according to the following chemical reaction: CO + H2O ⇌ CO2 + H2 While carbon dioxide is captured and removed through an adsorption process. The in-situ CO2 adsorption and removal shifts the water gas shift reaction to the right-hand side, thereby completely converting the CO and maximizing the production of high pressure hydrogen. Since the beginning of the second decade of the 21st century this technology has started gaining attention, as it shows advantages over carbon capture conventional technologies and because hydrogen is considered the energy carrier of the future. == Process == The SEWGS technology is the combination of the water gas shift reaction with the adsorption of carbon dioxide on a solid material. Typical temperature and pressure ranges are 350-550 °C and 20-30 bar. The inlet gas of SEWGS reactors is typically a mixture of hydrogen, CO and CO2, where steam is added to convert CO into


id: sorption-enhanced-water-gas-shift-20260505-1
file: data/en.wikipedia.org/wiki/Sorption_enhanced_water_gas_shift-1.md
category: reference
title: Sorption enhanced water gas shift
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sorption_enhanced_water_gas_shift
date_saved: 2026-05-05T10:50:41.661583+00:00
instance: kb-cron
parent: sorption-enhanced-water-gas-shift-20260505-0
summary:
== Applications == The importance of this technology is directly related to the problem of global warming and the mitigation of the carbon dioxide emissions. In hydrogen economy hydrogen is considered a clean energy carrier with high energy content and is expected to replace fossil fuels and other energy sources associated with pollution issues. For these reasons, since the beginning of second decade of the 21st century this technology attracted the public interest. The SEWGS technology enables producing high-purity hydrogen without need for further purification processes. It furthermore finds potential application in a wide range of industrial processes, such as in the production of electricity from fossil fuels or in the iron and steel industry. The integration of the SEWGS process in natural gas combined cycle (NGCC) and integrated gasification combined cycle (IGCC) power plants has been investigated as a possible way to produce electricity from natural gas or coal with almost-zero emissions. In NGCC power plant the carbon capture achieved is around 95% with a CO2 purity over 99%, while in IGCC power plants the carbon capture ratio is around 90% with a CO2 purity of 99%. The investigation of SEWGS integration in steel mills started during the second


id: sponge-iron-reaction-20260505-0
file: data/en.wikipedia.org/wiki/Sponge_iron_reaction-0.md
category: reference
title: Sponge iron reaction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sponge_iron_reaction
date_saved: 2026-05-05T10:50:42.820724+00:00
instance: kb-cron
parent: sponge-iron-reaction-20260505-0
summary:
The sponge iron reaction (SIR) is a chemical process based on redox cycling of an iron-based contact mass, the first cycle is a conversion step between iron metal (Fe) and wuestite (FeO), the second cycle is a conversion step between wuestite (FeO) and magnetite (Fe3O4). In application, the SIT is used in the reformer sponge iron cycle (RESC) in combination with a steam reforming unit. == Process description == The process has two modes, a reduction mode and an oxidation mode. === Iron-wuestite === FeO + H2 ↔ Fe + H2O === Magnetite-wuestite === Fe3O4 + H2 ↔ 3FeO + H2O == Application == The reformer sponge iron cycle is a two step cycle to produce hydrogen from hydrocarbon fuels based SIR and steam. === Reformer sponge iron cycle === In the first step the hydrocarbon fuel is reformed to syngas in the reformer which is then used to reduce the iron oxide (magnetite—Fe3O4) to iron (wüstite—FeO), in the second step steam is utilized to re-oxidise the iron into magnetite and hydrogen. The iron oxide pellets are placed in a pelletbed and have a service life of several thousand redox cycles. == See also == Packed bed Steam reforming ==


id: spontaneous-process-20260505-0
file: data/en.wikipedia.org/wiki/Spontaneous_process-0.md
category: reference
title: Spontaneous process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spontaneous_process
date_saved: 2026-05-05T10:50:43.996938+00:00
instance: kb-cron
parent: spontaneous-process-20260505-0
summary:
In thermodynamics, a spontaneous process is a process which occurs without any external input to the system. A more technical definition is the time-evolution of a system in which it releases free energy and it moves to a lower, more thermodynamically stable energy state (closer to thermodynamic equilibrium). The sign convention for free energy change follows the general convention for thermodynamic measurements, in which a release of free energy from the system corresponds to a negative change in the free energy of the system and a positive change in the free energy of the surroundings. Depending on the nature of the process, the free energy is determined differently. For example, the Gibbs free energy change is used when considering processes that occur under constant pressure and temperature conditions, whereas the Helmholtz free energy change is used when considering processes that occur under constant volume and temperature conditions. The value and even the sign of both free energy changes can depend upon the temperature and pressure or volume. Because spontaneous processes are characterized by a decrease in the system's free energy, they do not need to be driven by an outside source of energy. For cases involving an isolated system where


id: squalene-20260505-0
file: data/en.wikipedia.org/wiki/Squalene-0.md
category: reference
title: Squalene
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Squalene
date_saved: 2026-05-05T10:50:45.235356+00:00
instance: kb-cron
parent: squalene-20260505-0
summary:
Squalene is an organic compound. It is a triterpene with the formula C30H50. It is a colourless oil, although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as Squalus is a genus of sharks). An estimated 12% of bodily squalene in humans is found in sebum. Squalene has a role in topical skin lubrication and protection. Most plants, fungi, and animals produce squalene as biochemical precursor in sterol biosynthesis, including cholesterol and steroid hormones in the human body. It is also an intermediate in the biosynthesis of hopanoids in many bacteria. Squalene is an important ingredient in some vaccine adjuvants: The Novartis and GlaxoSmithKline adjuvants are called MF59 and AS03, respectively. == Role in triterpenoid synthesis == Squalene is a biochemical precursor to both steroids and hopanoids. For sterols, the squalene conversion begins with oxidation (via squalene monooxygenase) of one of its terminal double bonds, resulting in 2,3-oxidosqualene. It then undergoes an enzyme-catalysed cyclisation to produce lanosterol, which can be elaborated into other steroids such as cholesterol and ergosterol in a multistep process by the removal of three methyl groups, the reduction of one double bond by NADPH and the migration of the


id: staged-reforming-20260505-0
file: data/en.wikipedia.org/wiki/Staged_reforming-0.md
category: reference
title: Staged reforming
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Staged_reforming
date_saved: 2026-05-05T10:50:46.420855+00:00
instance: kb-cron
parent: staged-reforming-20260505-0
summary:
Staged reforming is a thermochemical process to convert organic material or bio waste such as wood, dung or hay into combustible gases containing methane, carbon monoxide and hydrogen. The single-stage reforming of bio materials results in high dust and tar yields in the produced gas restricting its use, hence the use of staged reforming. After reforming the output is approximately 80% fuel gas and 20% cokes. In staged reforming technology, gas conversion is a separate stage after pyrolysis. == First stage == Organic material is decomposed into gas and coal at approximately 600°C. == Second stage == Gas produced by the first stage is reformed with water vapor and heat energy from the cokes into a dust and residue-free fuel gas. Second stage process steps: Heating in the pre-heater at 1050°C. Cooldown in the reformer by chemical reaction at 750°C Further cooling to 550°C by heating the cold cokes by using cold mix Re-heating to 1050°C == See also == Plasma arc waste disposal Thermochemical conversion == References == == External links == Blauer Turm


id: starve-fed-20260505-0
file: data/en.wikipedia.org/wiki/Starve-fed-0.md
category: reference
title: Starve-fed
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Starve-fed
date_saved: 2026-05-05T10:50:47.632316+00:00
instance: kb-cron
parent: starve-fed-20260505-0
summary:
In emulsion polymerization, starve-fed refers to a method of monomer addition where the monomer is introduced gradually into the reaction vessel at a rate that allows the majority of monomer to be consumed by the reaction before more is added. The purpose of this method is generally to control the distribution of different monomers into a copolymer. Many monomers have different reaction rates and so, if all the monomers are added to the system at the same time, tend to react in blocks. This blockiness in the polymer leads to significantly different properties in the final polymer from one with a more statistically random distribution of monomers. This method is utilized in synthesizing core-shell latex particles by emulsion polymerization, in order to carefully prepare the final structure. == References ==


id: steam-reforming-20260505-0
file: data/en.wikipedia.org/wiki/Steam_reforming-0.md
category: reference
title: Steam reforming
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Steam_reforming
date_saved: 2026-05-05T10:50:48.851986+00:00
instance: kb-cron
parent: steam-reforming-20260505-0
summary:
Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly, natural gas is the feedstock. The main purpose of this technology is often hydrogen production, although syngas has multiple other uses such as production of ammonia or methanol. The reaction is represented by this equilibrium: CH 4 + H 2 O ↽ − − ⇀ CO + 3 H 2 {\displaystyle {\ce {CH4 + H2O <=> CO + 3 H2}}} The reaction is strongly endothermic (ΔHSR = 206 kJ/mol). Hydrogen produced by steam reforming is termed 'grey' hydrogen when the waste carbon dioxide is released to the atmosphere and 'blue' hydrogen when the carbon dioxide is (mostly) captured and stored geologically—see carbon capture and storage. Zero carbon 'green' hydrogen is produced by thermochemical water splitting, using solar thermal, low- or zero-carbon electricity or waste heat, or electrolysis, using low- or zero-carbon electricity. Zero carbon emissions 'turquoise' hydrogen is produced by one-step methane pyrolysis of natural gas. Steam reforming of natural gas produces most of the world's hydrogen. Hydrogen is used in the industrial synthesis of ammonia and other chemicals. == Reactions == Steam reforming reaction kinetics,


id: steam-reforming-20260505-1
file: data/en.wikipedia.org/wiki/Steam_reforming-1.md
category: reference
title: Steam reforming
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Steam_reforming
date_saved: 2026-05-05T10:50:48.851986+00:00
instance: kb-cron
parent: steam-reforming-20260505-0
summary:
The main difference between SMR and ATR is that SMR only uses air for combustion as a heat source to create steam, while ATR uses purified oxygen. The advantage of ATR is that the H2:CO ratio can be varied, which can be useful for producing specialty products. Due to the exothermic nature of some of the additional reactions occurring within ATR, the process can essentially be performed at a net enthalpy of zero (ΔH = 0). == Partial oxidation == Partial oxidation (POX) occurs when a sub-stoichiometric fuel-air mixture is partially combusted in a reformer creating hydrogen-rich syngas. POX is typically much faster than steam reforming and requires a smaller reactor vessel. POX produces less hydrogen per unit of the input fuel than steam reforming of the same fuel. == Steam reforming at small scale == The capital cost of steam reforming plants is considered prohibitive for small to medium size applications. The costs for these elaborate facilities do not scale down well. Conventional steam reforming plants operate at pressures between 200 and 600 psi (14–40 bar) with outlet temperatures in the range of 815 to 925 °C. === For combustion engines === Flared gas and vented volatile organic compounds


id: strontian-process-20260505-0
file: data/en.wikipedia.org/wiki/Strontian_process-0.md
category: reference
title: Strontian process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Strontian_process
date_saved: 2026-05-05T10:50:50.012986+00:00
instance: kb-cron
parent: strontian-process-20260505-0
summary:
The strontian process is an obsolete chemical method to recover sugar from molasses. Its use in Europe peaked in the middle of the 19th century. The name strontian comes from the Scottish village Strontian where the source mineral strontianite (strontium carbonate) was first found. == Chemistry == Strontium carbonate is a recycled coreactant in this process. Strontium carbonate is calcined with carbon in the presence of steam to form strontium hydroxide. The strontium and carbon dioxide formed are rejoined later in the process, forming strontium carbonate once again. SrCO3 + C + H2O + O2 = Sr(OH)2 + 2 CO2 In a molasses solution kept near 100 °C, the hydroxide reacts with soluble sugars to form water and the poorly soluble strontium saccharide which is filtered out, but kept awash in near-boiling water. Sr(OH)2 + 2C12H22O11 = SrO(C12H22O11)2 + H2O The saccharate liquid is cooled to 10 °C, cracking off one of the sugars SrO(C12H22O11)2 = SrO(C12H22O11) + C12H22O11 The carbon dioxide (from the calcination) is bubbled through the saccharate solution, cracking off the second sugar and reforming the strontium carbonate, which is filtered off. SrO(C12H22O11) + CO2 = SrCO3 + C12H22O11 The sugar is then extracted through evaporating the


id: sublimation-phase-transition-20260505-0
file: data/en.wikipedia.org/wiki/Sublimation_(phase_transition)-0.md
category: reference
title: Sublimation (phase transition)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sublimation_(phase_transition)
date_saved: 2026-05-05T10:50:51.150506+00:00
instance: kb-cron
parent: sublimation-phase-transition-20260505-0
summary:
Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the intermediate liquid state. The verb form of sublimation is sublime, or less preferably, sublimate. Sublimate also refers to the product obtained by sublimation. The point at which sublimation occurs rapidly (for further details, see below) is called critical sublimation point, or simply sublimation point. Notable examples include sublimation of dry ice at room temperature and atmospheric pressure, and that of solid iodine with heating. The reverse process of sublimation is deposition (also called desublimation), in which a substance passes directly from a gas to a solid phase, without passing through the intermediate liquid state. Technically, all solids may sublime, though most sublime at extremely low rates that are hardly detectable under usual conditions. At normal pressures, most chemical compounds and elements possess three different states at different temperatures. In these cases, the transition from the solid to the gas state requires an intermediate liquid state. The pressure referred to is the partial pressure of the substance, not the total (e.g. atmospheric) pressure of the entire system. Thus, any solid can sublime if its vapour pressure is higher than the surrounding partial


id: sublimation-phase-transition-20260505-1
file: data/en.wikipedia.org/wiki/Sublimation_(phase_transition)-1.md
category: reference
title: Sublimation (phase transition)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sublimation_(phase_transition)
date_saved: 2026-05-05T10:50:51.150506+00:00
instance: kb-cron
parent: sublimation-phase-transition-20260505-0
summary:
At atmospheric pressure, arsenic sublimes gradually upon heating, and sublimes rapidly at 887 K (614 °C). Cadmium and zinc sublime much more than other common materials, so they are not suitable materials for use in vacuum. == Purification by sublimation == Sublimation is a technique used by chemists to purify compounds. A solid is typically placed in a sublimation apparatus and heated under vacuum. Under this reduced pressure, the solid volatilizes and condenses as a purified compound on a cooled surface (cold finger), leaving a non-volatile residue of impurities behind. Once heating ceases and the vacuum is removed, the purified compound may be collected from the cooling surface. For even higher purification efficiencies, a temperature gradient is applied, which also allows for the separation of different fractions. Typical setups use an evacuated glass tube that is heated gradually in a controlled manner. The material flow is from the hot end, where the initial material is placed, to the cold end that is connected to a pump stand. By controlling temperatures along the length of the tube, the operator can control the zones of re-condensation, with very volatile compounds being pumped out of the system completely (or caught by a separate


id: substrate-materials-science-20260505-0
file: data/en.wikipedia.org/wiki/Substrate_(materials_science)-0.md
category: reference
title: Substrate (materials science)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Substrate_(materials_science)
date_saved: 2026-05-05T10:50:52.314734+00:00
instance: kb-cron
parent: substrate-materials-science-20260505-0
summary:
Substrate is a term used in materials science and engineering to describe the base material on which processing is conducted. Surfaces have different uses, including producing new film or layers of material and being a base to which another substance is bonded. == Description == In materials science and engineering, a substrate refers to a base material on which processing is conducted. This surface could be used to produce new film or layers of material such as deposited coatings. It could be the base to which paint, adhesives, or adhesive tape is bonded. A typical substrate might be rigid such as metal, concrete, or glass, onto which a coating might be deposited. Flexible substrates are also used. Some substrates are anisotropic with surface properties being different depending on the direction: examples include wood and paper products. == Coatings == With all coating processes, the condition of the surface of the substrate can strongly affect the bond of subsequent layers. This can include cleanliness, smoothness, surface energy, moisture, etc. Coating can be by a variety of processes, including: Adhesives and adhesive tapes Coating and printing processes Chemical vapor deposition and physical vapor deposition Conversion coating Anodizing Chromate conversion coating Plasma electrolytic


id: sulfite-process-20260505-0
file: data/en.wikipedia.org/wiki/Sulfite_process-0.md
category: reference
title: Sulfite process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sulfite_process
date_saved: 2026-05-05T10:50:53.758525+00:00
instance: kb-cron
parent: sulfite-process-20260505-0
summary:
The sulfite process produces wood pulp that is almost pure cellulose fibers by treating wood chips with solutions of sulfite and bisulfite ions. These chemicals cleave the bonds between the cellulose and lignin components of the lignocellulose. A variety of sulfite/bisulfite salts are used, including sodium (Na+), calcium (Ca2+), potassium (K+), magnesium (Mg2+), and ammonium (NH4+). The lignin is converted to lignosulfonates, which are soluble and can be separated from the cellulose fibers. For the production of cellulose, the sulfite process competes with the Kraft process which produces stronger fibers and is less environmentally costly. == History == The use of wood to make pulp for paper began with the development of mechanical pulping in the 1840s by Charles Fenerty in Nova Scotia and by F. G. Keller in Germany. Chemical processes quickly followed, first with Julius Roth's use of sulfurous acid to treat wood in 1857, followed by Benjamin Chew Tilghman's US patent on the use of calcium bisulfite, Ca(HSO3)2, to pulp wood in 1867. Almost a decade later in 1874 the first commercial sulfite pulp mill was built in Sweden. It used magnesium as the counter ion and was based on work by Carl Daniel Ekman. By 1900


id: sulfite-process-20260505-1
file: data/en.wikipedia.org/wiki/Sulfite_process-1.md
category: reference
title: Sulfite process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sulfite_process
date_saved: 2026-05-05T10:50:53.758525+00:00
instance: kb-cron
parent: sulfite-process-20260505-0
summary:
== Applications == The sulfite process is acidic and one of the drawbacks is that the acidic conditions hydrolyze some of the cellulose, which means that sulfite pulp fibers are not as strong as kraft pulp fibers. The yield of pulp (based on wood used) is higher than for kraft pulping and sulfite pulp is easier to bleach. === Commodity === Sulfite pulp remains an important commodity, especially for specialty papers and as a source of cellulose for non-paper applications. It is used to make fine paper, tissue, glassine, and to add strength to newsprint. === Dissolving pulp === A special grade of bleached sulfite pulp is known as dissolving pulp which is the raw material for a wide variety of cellulose derivatives, for example rayon, cellophane, cellulose acetate and methylcellulose. Rayon is a reconstituted cellulose fiber used to make many fabrics. Cellophane is a clear reconstituted cellulose film used in wrapping and windows in envelopes. Cellulose acetate was used to make flexible films for photographic use, computer tapes and so on and also to make fibers. Methylcellulose and other cellulose ether derivatives are used in a wide range of everyday products from adhesives to baked goods to pharmaceuticals. ==


id: sulfur-vulcanization-20260505-0
file: data/en.wikipedia.org/wiki/Sulfur_vulcanization-0.md
category: reference
title: Sulfur vulcanization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sulfur_vulcanization
date_saved: 2026-05-05T10:51:10.061530+00:00
instance: kb-cron
parent: sulfur-vulcanization-20260505-0
summary:
Sulfur vulcanization is a chemical process for converting natural rubber or related polymers into materials of varying hardness, elasticity, and mechanical durability by heating them with sulfur or sulfur-containing compounds. Sulfur forms cross-linking bridges between sections of polymer chains which affects the mechanical properties. Many products are made with vulcanized rubber, including tires, shoe soles, hoses, and conveyor belts. The term vulcanization is derived from Vulcan, the Roman god of fire. The main polymers subjected to sulfur vulcanization are polyisoprene (natural rubber, NR), polybutadiene rubber (BR) and styrene-butadiene rubber (SBR), and ethylene propylene diene monomer rubber (EPDM rubber). All of these materials contain alkene groups adjacent to methylene groups. Other specialty rubbers may also be vulcanized, such as nitrile rubber (NBR) and butyl rubber (IIR). Vulcanization, in common with the curing of other thermosetting polymers, is generally irreversible. Efforts have focused on developing de-vulcanization (see tire recycling) processes for recycling of rubber waste but with little success. == Structural and mechanistic details == The details of vulcanization remain murky because the process converts mixtures of polymers to mixtures of insoluble derivatives. By design the reaction does not proceed to completion because a fully crosslinked polymer would be too rigid for


id: sulfur-vulcanization-20260505-1
file: data/en.wikipedia.org/wiki/Sulfur_vulcanization-1.md
category: reference
title: Sulfur vulcanization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sulfur_vulcanization
date_saved: 2026-05-05T10:51:10.061530+00:00
instance: kb-cron
parent: sulfur-vulcanization-20260505-0
summary:
Secondary accelerants have very fast vulcanization speeds with minimal induction time, making them unsuitable as primary accelerants in highly unsaturated rubbers such as NR or SBR. However, they can be used as primary accelerants in compounds with fewer curing site such as EPDM. Xanthates (principally, zinc isopropyl xanthate) are important in the vulcanization of latex, which is cured at relatively low temperatures (100-120 °C), and therefore needs an inherently rapid accelerant. The major thiurams used are TMTD (tetramethylthiuram disulfide) and TETD (tetraethylthiuram disulfide). The major dithiocarbamates are the zinc salts ZDMC (zinc dimethyldithiocarbamate), ZDEC (zinc diethyldithiocarbamate) and ZDBC (zinc dibutyldithiocarbamate). === Activators === Activators consist of various metal salts, fatty acids, as well as nitrogen-containing bases, the most important these being zinc oxide. Zinc activates many accelerants by coordination, for example causing thiuram to convert into ziram. Zinc also coordinates to the sulfur-chains of sulfurating agents, changing the most likely bond to break during cross-link formation. Ultimately, activators promote the efficient use of sulfur to give a high density of cross-links. Due to the low solubility of ZnO it is often combined with fatty acids such as stearic acid to form more soluble metallic soap, i.e., zinc stearate. === Retarders


id: sulfur-vulcanization-20260505-2
file: data/en.wikipedia.org/wiki/Sulfur_vulcanization-2.md
category: reference
title: Sulfur vulcanization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Sulfur_vulcanization
date_saved: 2026-05-05T10:51:10.061530+00:00
instance: kb-cron
parent: sulfur-vulcanization-20260505-0
summary:
He directly inferred that if the process of charring could be stopped at the right point, it might divest the gum of its native adhesiveness throughout, which would make it better than the native gum. Upon further trial with heat, he was further convinced of the correctness of this inference, by finding that the India rubber could not be melted in boiling sulfur at any heat, but always charred. He made another trial of heating a similar fabric before an open fire. The same effect, that of charring the gum, followed. There were further indications of success in producing the desired result, as upon the edge of the charred portion appeared a line or border, that was not charred, but perfectly cured. Goodyear then goes on to describe how he moved to Woburn, Massachusetts and carried out a series of systematic experiments to optimize the curing of rubber, collaborating with Nathaniel Hayward. On ascertaining to a certainty that he had found the object of his search and much more, and that the new substance was proof against cold and the solvent of the native gum, he felt himself amply repaid for the past, and quite indifferent to the trials of


id: syneresis-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Syneresis_(chemistry)-0.md
category: reference
title: Syneresis (chemistry)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Syneresis_(chemistry)
date_saved: 2026-05-05T10:51:11.242016+00:00
instance: kb-cron
parent: syneresis-chemistry-20260505-0
summary:
Syneresis (also spelled 'synæresis' or 'synaeresis'), in chemistry, is the extraction or expulsion of a liquid from a gel, such as when serum drains from a contracting clot of blood. Another example of syneresis is the collection of whey on the surface of yogurt. Syneresis can also be observed when the amount of diluent in a swollen polymer exceeds the solubility limit as the temperature changes. A household example of this is the counterintuitive expulsion of water from dry gelatin when the temperature increases. Syneresis has also been proposed as the mechanism of formation for the amorphous silica composing the frustule of diatoms. == Examples == In the processing of dairy milk, for example during cheese making, syneresis is the formation of the curd due to the sudden removal of the hydrophilic macropeptides, which causes an imbalance in intermolecular forces. Bonds between hydrophobic sites start to develop and are enforced by calcium bonds, which form as the water molecules in the micelles start to leave the structure. This process is usually referred to as the phase of coagulation and syneresis. The splitting of the bond between residues 105 and 106 in the κ-casein molecule is often called the primary phase


id: tank-blanketing-20260505-0
file: data/en.wikipedia.org/wiki/Tank_blanketing-0.md
category: reference
title: Tank blanketing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Tank_blanketing
date_saved: 2026-05-05T10:51:12.410912+00:00
instance: kb-cron
parent: tank-blanketing-20260505-0
summary:
Tank blanketing, also called gas sealing or tank padding, is the process of applying a gas to the space above the liquid level in a storage container such as a tank. Tank blanketing is used for a variety of reasons, including protecting products quality by reducing oxidation, longer product life, reduced fire and explosion hazards, and longer equipment life cycles. == Methods == The basic concept is to introduce the blanketing gas into the system, and to vent the gas should the pressure get too high. this is usually accomplished by automatic gas control valves with controls referenced to the tank pressure. The vapor pressure inside the container can decrease if the liquid inside the container is removed (i.e., drained or pumped), or if the environmental temperature decreases resulting in a decrease in liquid and vapor temperature, or if the liquid is cooled by process or natural heat transfer from an initially hot liquid. If the vapor pressure drops below the pad valve set point, the pad valve opens and allows the blanketing gas to enter. Once the pressure reaches the set point, the pad valve closes. The tank vapor pressure can increase if liquid is added, or if the


id: telomerization-20260505-0
file: data/en.wikipedia.org/wiki/Telomerization-0.md
category: reference
title: Telomerization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Telomerization
date_saved: 2026-05-05T10:51:13.669879+00:00
instance: kb-cron
parent: telomerization-20260505-0
summary:
Telomerization is a reaction that produces a particular kind of oligomer with two distinct end groups. The oligomer is called a telomer. Some telomerizations proceed by radical pathways, many do not. A generic equation is: A−B + nM → A−Mn−B where M is the monomer, and A and B are the end groups, and n is the degree of polymerization. One example is the coupled dimerization and hydroesterification of buta-1,3-diene. This step produces a doubly unsaturated C9-ester: 2 CH2=CH-CH=CH2 + CO + CH3OH → CH2=CH(CH2)3CH=CHCH2CO2CH3 The monomer in this reaction is butadiene, the degree of polymerization is 2, and the end groups are vinyl and the carboxy methyl (CO2CH3). This and several related reactions proceed with palladium catalysts. Many telomerizations are used in industrial chemistry. == Nomenclature == According to the jargon in polymer chemistry, telomerization requires a telogen to react with at least one unsaturated taxogen molecule. Fluorotelomers are an example. == See also == Perfluorooctanoic acid (synthesis) Telomerization (dimerization) == References ==


id: thermal-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Thermal_analysis-0.md
category: reference
title: Thermal analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermal_analysis
date_saved: 2026-05-05T10:51:14.889227+00:00
instance: kb-cron
parent: thermal-analysis-20260505-0
summary:
Thermal analysis is a branch of materials science where the properties of materials are studied as they change with temperature. Several methods are commonly used – these are distinguished from one another by the property which is measured: Dielectric thermal analysis: dielectric permittivity and loss factor Differential thermal analysis: temperature difference versus temperature or time Differential scanning calorimetry: heat flow changes versus temperature or time Dilatometry: volume changes with temperature change Dynamic mechanical analysis: measures storage modulus (stiffness) and loss modulus (damping) versus temperature, time and frequency Evolved gas analysis: analysis of gases evolved during heating of a material, usually decomposition products Isothermal titration calorimetry Isothermal microcalorimetry Laser flash analysis: thermal diffusivity and thermal conductivity Thermogravimetric analysis: mass change versus temperature or time Thermomechanical analysis: dimensional changes versus temperature or time Thermo-optical analysis: optical properties Derivatography: A complex method in thermal analysis Simultaneous thermal analysis generally refers to the simultaneous application of thermogravimetry and differential scanning calorimetry to one and the same sample in a single instrument. The test conditions are perfectly identical for the thermogravimetric analysis and differential scanning calorimetry signals (same atmosphere, gas flow rate, vapor pressure of the sample, heating rate, thermal contact to the sample crucible


id: thermal-analysis-20260505-1
file: data/en.wikipedia.org/wiki/Thermal_analysis-1.md
category: reference
title: Thermal analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermal_analysis
date_saved: 2026-05-05T10:51:14.889227+00:00
instance: kb-cron
parent: thermal-analysis-20260505-0
summary:
== Metals == Production of many metals (cast iron, grey iron, ductile iron, compacted graphite iron, 3000 series aluminium alloys, copper alloys, silver, and complex steels) are aided by a production technique also referred to as thermal analysis. A sample of liquid metal is removed from the furnace or ladle and poured into a sample cup with a thermocouple embedded in it. The temperature is then monitored, and the phase diagram arrests (liquidus, eutectic, and solidus) are noted. From this information chemical composition based on the phase diagram can be calculated, or the crystalline structure of the cast sample can be estimated especially for silicon morphology in hypo-eutectic Al-Si cast alloys. Strictly speaking these measurements are cooling curves and a form of sample controlled thermal analysis whereby the cooling rate of the sample is dependent on the cup material (usually bonded sand) and sample volume which is normally a constant due to the use of standard sized sample cups. To detect phase evolution and corresponding characteristic temperatures, cooling curve and its first derivative curve should be considered simultaneously. Examination of cooling and derivative curves is done by using appropriate data analysis software. The process consists of plotting, smoothing and curve


id: thermal-cleaning-20260505-0
file: data/en.wikipedia.org/wiki/Thermal_cleaning-0.md
category: reference
title: Thermal cleaning
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermal_cleaning
date_saved: 2026-05-05T10:51:16.038429+00:00
instance: kb-cron
parent: thermal-cleaning-20260505-0
summary:
Thermal cleaning is a combined process involving pyrolysis and oxidation. As an industrial application, thermal cleaning is used to remove organic substances such as polymers, plastics and coatings from parts, products or production components like extruder screws, spinnerets and static mixers. Thermal cleaning is the most common cleaning method in industrial environment. A variety of different methods have been developed so far for a wide range of applications. == Process == Heat is supplied for pyrolysis and air is supplied for oxidation. Depending on the procedure, pyrolysis and oxidation can be applied consecutively or simultaneously. During thermal cleaning, organic material is converted into volatile organic compounds, hydrocarbons and carbonized gas. Inorganic elements remain. Typical process temperatures range between 400 and 540 °C (752 and 1,004 °F). Several types of industrial thermal cleaning systems are available: === Fluidized bed systems === Fluidized bed systems use sand or aluminium oxide (alumina) as heating medium. They apply pyrolysis and oxidation simultaneously. These systems clean fast, from 30 minutes process time up to two hours. The medium does not melt or boil, nor emit any vapors or odors. Thermal shock can be a problem with some parts. Pollution control devices may be needed to


id: thermal-dissolution-20260505-0
file: data/en.wikipedia.org/wiki/Thermal_dissolution-0.md
category: reference
title: Thermal dissolution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermal_dissolution
date_saved: 2026-05-05T10:51:17.218646+00:00
instance: kb-cron
parent: thermal-dissolution-20260505-0
summary:
Thermal dissolution is a method of liquefaction of solid fossil fuels. It is a hydrogen-donor solvent refining process. It may be used for the shale oil extraction and coal liquefaction. Other liquids extraction processes from solid fuels are pyrolysis and hydrogenation. Compared to hydrogenation, the process of thermal dissolution has milder conditions, simpler process, and no consumption of catalyst. == References ==


id: thermal-spraying-20260505-0
file: data/en.wikipedia.org/wiki/Thermal_spraying-0.md
category: reference
title: Thermal spraying
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermal_spraying
date_saved: 2026-05-05T10:51:18.428017+00:00
instance: kb-cron
parent: thermal-spraying-20260505-0
summary:
Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame). Thermal spraying can provide thick coatings (approx. thickness range is 20 microns to several mm, depending on the process and feedstock), over a large area at high deposition rate as compared to other coating processes such as electroplating, physical and chemical vapor deposition. Coating materials available for thermal spraying include metals, alloys, ceramics, plastics and composites. They are fed in powder or wire form, heated to a molten or semimolten state and accelerated towards substrates in the form of micrometer-size particles. Combustion or electrical arc discharge is usually used as the source of energy for thermal spraying. Resulting coatings are made by the accumulation of numerous sprayed particles. The surface may not heat up significantly, allowing the coating of flammable substances. Coating quality is usually assessed by measuring its porosity, oxide content, macro and micro-hardness, bond strength and surface roughness. Generally, the coating quality increases with increasing particle velocities. == Variations == Several variations of thermal spraying are distinguished: Plasma spraying Detonation spraying Wire arc spraying Flame


id: thermal-spraying-20260505-1
file: data/en.wikipedia.org/wiki/Thermal_spraying-1.md
category: reference
title: Thermal spraying
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermal_spraying
date_saved: 2026-05-05T10:51:18.428017+00:00
instance: kb-cron
parent: thermal-spraying-20260505-0
summary:
Direct current (DC plasma), where the energy is transferred to the plasma jet by a direct current, high-power electric arc Induction plasma or RF plasma, where the energy is transferred by induction from a coil around the plasma jet, through which an alternating, radio-frequency current passes Plasma-forming medium: Gas-stabilized plasma (GSP), where the plasma forms from a gas; typically argon, hydrogen, helium or their mixtures Water-stabilized plasma (WSP), where plasma forms from water (through evaporation, dissociation and ionization) or other suitable liquid Hybrid plasma – with combined gas and liquid stabilization, typically argon and water Spraying environment: Atmospheric plasma spraying (APS), performed in ambient air Controlled atmosphere plasma spraying (CAPS), usually performed in a closed chamber, either filled with inert gas or evacuated Variations of CAPS: high-pressure plasma spraying (HPPS), low-pressure plasma spraying (LPPS), the extreme case of which is vacuum plasma spraying (VPS, see below) Underwater plasma spraying Another variation consists of having a liquid feedstock instead of a solid powder for melting, this technique is known as Solution precursor plasma spray === Vacuum plasma spraying === Vacuum plasma spraying (VPS) is a technology for etching and surface modification to create porous layers with high reproducibility and for cleaning


id: thermal-spraying-20260505-2
file: data/en.wikipedia.org/wiki/Thermal_spraying-2.md
category: reference
title: Thermal spraying
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermal_spraying
date_saved: 2026-05-05T10:51:18.428017+00:00
instance: kb-cron
parent: thermal-spraying-20260505-0
summary:
During the 1980s, a class of thermal spray processes called high velocity oxy-fuel spraying was developed. A mixture of gaseous or liquid fuel and oxygen is fed into a combustion chamber, where they are ignited and combusted continuously. The resultant hot gas at a pressure close to 1 MPa (10 bar; 150 psi) emanates through a converging–diverging nozzle and travels through a straight section. The fuels can be gases (hydrogen, methane, propane, propylene, acetylene, natural gas, etc.) or liquids (kerosene, etc.). The jet velocity at the exit of the barrel (>1,000 m/s (3,300 ft/s)) exceeds the speed of sound. A powder feed stock is injected into the gas stream, which accelerates the powder up to 800 m/s (2,600 ft/s). The stream of hot gas and powder is directed towards the surface to be coated. The powder partially melts in the stream, and deposits upon the substrate. The resulting coating has low porosity and high bond strength. HVOF coatings may be as thick as 12 mm (1⁄2 in). It is typically used to deposit wear and corrosion resistant coatings on materials, such as ceramic and metallic layers. Common powders include WC-Co, chromium carbide, MCrAlY, and alumina. The process has been most


id: thermal-spraying-20260505-3
file: data/en.wikipedia.org/wiki/Thermal_spraying-3.md
category: reference
title: Thermal spraying
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermal_spraying
date_saved: 2026-05-05T10:51:18.428017+00:00
instance: kb-cron
parent: thermal-spraying-20260505-0
summary:
== Limitations == Thermal spraying is a line of sight process and the bond mechanism is primarily mechanical. Thermal spray application is not compatible with the substrate if the area to which it is applied is complex or blocked by other bodies. == Safety == Thermal spraying need not be a dangerous process if the equipment is treated with care and correct spraying practices are followed. As with any industrial process, there are a number of hazards of which the operator should be aware and against which specific precautions should be taken. Ideally, equipment should be operated automatically in enclosures specially designed to extract fumes, reduce noise levels, and prevent direct viewing of the spraying head. Such techniques will also produce coatings that are more consistent. There are occasions when the type of components being treated, or their low production levels, require manual equipment operation. Under these conditions, a number of hazards peculiar to thermal spraying are experienced in addition to those commonly encountered in production or processing industries. === Noise === Metal spraying equipment uses compressed gases which create noise. Sound levels vary with the type of spraying equipment, the material being sprayed, and the operating parameters. Typical sound


id: transfer-hydrogenation-20260505-0
file: data/en.wikipedia.org/wiki/Transfer_hydrogenation-0.md
category: reference
title: Transfer hydrogenation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transfer_hydrogenation
date_saved: 2026-05-05T10:51:19.589468+00:00
instance: kb-cron
parent: transfer-hydrogenation-20260505-0
summary:
In chemistry, transfer hydrogenation is a chemical reaction involving the addition of hydrogen to a compound from a source other than molecular H2. It is applied in laboratory and industrial organic synthesis to saturate organic compounds and reduce ketones to alcohols, and imines to amines. It avoids the need for high-pressure molecular H2 used in conventional hydrogenation. Transfer hydrogenation usually occurs at mild temperature and pressure conditions using organic or organometallic catalysts, many of which are chiral, allowing efficient asymmetric synthesis. It uses hydrogen donor compounds such as formic acid, isopropanol or dihydroanthracene, dehydrogenating them to CO2, acetone, or anthracene respectively. Often, the donor molecules also function as solvents for the reaction. A large scale application of transfer hydrogenation is coal liquefaction using "donor solvents" such as tetralin. == Organometallic catalysts == In the area of organic synthesis, a useful family of hydrogen-transfer catalysts have been developed based on ruthenium and rhodium complexes, often with diamine and phosphine ligands. A representative catalyst precursor is derived from (cymene)ruthenium dichloride dimer and the tosylated diphenylethylenediamine. These catalysts are mainly employed for the reduction of ketones and imines to alcohols and amines, respectively. The hydrogen-donor (transfer agent) is typically isopropanol, which converts to


id: trituration-20260505-0
file: data/en.wikipedia.org/wiki/Trituration-0.md
category: reference
title: Trituration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Trituration
date_saved: 2026-05-05T10:51:20.734473+00:00
instance: kb-cron
parent: trituration-20260505-0
summary:
Trituration (Latin, grinding) is the name of several different methods used to process materials. In one sense, it is a form of comminution (reducing the particle size of a substance). In another sense, it is the production of a homogeneous powdered material by mixing and grinding component materials thoroughly. For example, a dental amalgam is formed by combining particles of a metal, usually gold or silver, with mercury. In organic chemistry, trituration is a process used to purify crude chemical compounds containing soluble impurities. A solvent is chosen in which the desired product is insoluble and the undesired by-products are very soluble or vice versa. For example, when the impurities are soluble and the desired product is not, the crude material is washed with the solvent and filtered, leaving the purified product in solid form and any impurities in solution. If mixed solvents are used, target compound and impurities are first dissolved in small amount of solvent, and then addition of another solvent causes desired compound to precipitate. This can be considered a crude form of recrystallization performed without changes in temperature. In pharmacy, trituration can also refer to the process of grinding one compound into another to dilute one


id: umpolung-20260505-0
file: data/en.wikipedia.org/wiki/Umpolung-0.md
category: reference
title: Umpolung
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Umpolung
date_saved: 2026-05-05T10:51:21.935827+00:00
instance: kb-cron
parent: umpolung-20260505-0
summary:
In organic chemistry, umpolung (German: [ˈʔʊmˌpoːlʊŋ]) or polarity inversion is the chemical modification of a functional group with the aim of the reversal of polarity of that group. This modification allows secondary reactions of this functional group that would otherwise not be possible. The concept was introduced by D. Seebach (hence the German word umpolung for reversed polarity) and E.J. Corey. Polarity analysis during retrosynthetic analysis tells a chemist when umpolung tactics are required to synthesize a target molecule. == Introduction == The vast majority of important organic molecules contain heteroatoms, which polarize carbon skeletons by virtue of their electronegativity. Therefore, in standard organic reactions, the majority of new bonds are formed between atoms of opposite polarity. This can be considered to be the "normal" mode of reactivity. One consequence of this natural polarization of molecules is that 1,3- and 1,5- heteroatom substituted carbon skeletons are extremely easy to synthesize (Aldol reaction, Claisen condensation, Michael reaction, Claisen rearrangement, Diels-Alder reaction), whereas 1,2-, 1,4-, and 1,6- heteroatom substitution patterns are more difficult to access via "normal" reactivity. It is therefore important to understand and develop methods to induce umpolung in organic reactions. == Examples == The simplest method of obtaining 1,2-,


id: umpolung-20260505-1
file: data/en.wikipedia.org/wiki/Umpolung-1.md
category: reference
title: Umpolung
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Umpolung
date_saved: 2026-05-05T10:51:21.935827+00:00
instance: kb-cron
parent: umpolung-20260505-0
summary:
Dithiane chemistry opens the way to many new chemical transformations. One example is found in so-called anion relay chemistry in which a negative charge of an anionic functional group resulting from one organic reaction is transferred to a different location within the same carbon framework and available for secondary reaction. In this example of a multi-component reaction both formaldehyde (1) and isopropylaldehyde (8) are converted into dithianes 3 and 9 with 1,3-propanedithiol. Sulfide 3 is first silylated by reaction with tert-butyllithium and then trimethylsilyl chloride 4 and then the second acyl proton is removed and reacted with optically active (−)-epichlorohydrin 6 replacing chlorine. This compound serves as the substrate for reaction with the other dithiane 9 to the oxirane ring opening product 10. Under influence of the polar base HMPA, 10 rearranges in a 1,4-Brook rearrangement to the silyl ether 11 reactivating the formaldehyde dithiane group as an anion (hence the anion relay concept). This dithiane group reacts with oxirane 12 to the alcohol 13 and in the final step the sulfide groups are removed with (bis(trifluoroacetoxy)iodo)benzene. The anion relay chemistry tactic has been applied elegantly in the total synthesis of complex molecules of significant biological activity, such as spongistatin


id: urea-extraction-crystallization-20260505-0
file: data/en.wikipedia.org/wiki/Urea_extraction_crystallization-0.md
category: reference
title: Urea extraction crystallization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Urea_extraction_crystallization
date_saved: 2026-05-05T10:51:23.142083+00:00
instance: kb-cron
parent: urea-extraction-crystallization-20260505-0
summary:
The urea extraction crystallization is a process for separating linear paraffins (n-paraffins, n-alkanes) from hydrocarbon mixtures through the formation of urea-n-paraffin-clathrates. The process is primarily used to lower the pour point of petroleum products, by-products of the process are n-paraffins in high purity. The method may also applied for the separation of fatty acids and fatty alcohols. In addition to urea also thiourea is used in the process. == History == In 1939 German chemist Friedrich Bergen was trying different extractants to separate serum proteins from milk at low temperature. When he tried urea, he noticed that something unusual was going on with milk lipids. A treatment with octanol serendipitously revealed that it combines with urea in large crystals. Bergen investigated different lipids, alkanes and alcohols and found out that at least six carbon atoms are required, and that branched hydrocarbons don't participate in the phenomenon. Not being an expert in hydrocarbons and urea, he cooperated with Matthias Pier from BASF/IG Farben and then with Wilhelm Schlenk, filing for patents with the latter in 1940, which were awarded in 1953. They didn't publish their findings until 1949 because German authorities classified the discovery during the World War II, but the


id: vapor-compression-evaporation-20260505-0
file: data/en.wikipedia.org/wiki/Vapor-compression_evaporation-0.md
category: reference
title: Vapor-compression evaporation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor-compression_evaporation
date_saved: 2026-05-05T10:51:24.318230+00:00
instance: kb-cron
parent: vapor-compression-evaporation-20260505-0
summary:
Vapor-compression evaporation is the evaporation method by which a blower, compressor or jet ejector is used to compress, and thus, increase the pressure of the vapor produced. Since the pressure increase of the vapor also generates an increase in the condensation temperature, the same vapor can serve as the heating medium for its "mother" liquid or solution being concentrated, from which the vapor was generated to begin with. If no compression was provided, the vapor would be at the same temperature as the boiling liquid/solution, and no heat transfer could take place. It is also sometimes called vapor compression distillation (VCD). If compression is performed by a mechanically driven compressor or blower, this evaporation process is usually referred to as MVR (mechanical vapor recompression). In case of compression performed by high pressure motive steam ejectors, the process is usually called thermocompression, steam compression or ejectocompression. == MVR process == === Energy input === In this case the energy input to the system lies in the pumping energy of the compressor. The theoretical energy consumption will be equal to E = Q ∗ ( H 2 − H 1 ) {\displaystyle E=Q*(H2-H1)} , where E is the total theoretical pumping energy


id: vapor-compression-evaporation-20260505-1
file: data/en.wikipedia.org/wiki/Vapor-compression_evaporation-1.md
category: reference
title: Vapor-compression evaporation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor-compression_evaporation
date_saved: 2026-05-05T10:51:24.318230+00:00
instance: kb-cron
parent: vapor-compression-evaporation-20260505-0
summary:
== Efficiency == The efficiency and feasibility of this process depends on the efficiency of the compressing device (e.g., blower, compressor or steam ejector) and the heat transfer coefficient attained in the heat exchanger contacting the condensing vapor and the boiling "mother" solution/liquid. Theoretically, if the resulting condensate is subcooled, this process could allow full recovery of the latent heat of vaporization that would otherwise be lost if the vapor, rather than the condensate, was the final product; therefore, this method of evaporation is very energy efficient. The evaporation process may be solely driven by the mechanical work provided by the compressing device. == Some uses == === Clean water production === A vapor-compression evaporator, like most evaporators, can make reasonably clean water from any water source. In a salt crystallizer, for example, a typical analysis of the resulting condensate shows a typical content of residual salt not higher than 50 ppm or, in terms of electrical conductance, not higher than 10 μS/cm. This results in a drinkable water, if the other sanitary requirements are fulfilled. While this cannot compete in the marketplace with reverse osmosis or demineralization, vapor compression chiefly differs from these thanks to its ability to make


id: vapor-compression-refrigeration-20260505-0
file: data/en.wikipedia.org/wiki/Vapor-compression_refrigeration-0.md
category: reference
title: Vapor-compression refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor-compression_refrigeration
date_saved: 2026-05-05T10:51:25.495110+00:00
instance: kb-cron
parent: vapor-compression-refrigeration-20260505-0
summary:
Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air conditioning of buildings and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services. Oil refineries, petrochemical and chemical processing plants, and natural gas processing plants are among the many types of industrial plants that often utilize large vapor-compression refrigeration systems. Cascade refrigeration systems may also be implemented using two compressors. Refrigeration may be defined as lowering the temperature of an enclosed space by removing heat from that space and transferring it elsewhere. A device that performs this function may also be called an air conditioner, refrigerator, air source heat pump, geothermal heat pump, or chiller (heat pump). == Description == Vapor-compression uses a circulating liquid refrigerant as the medium which absorbs and removes heat from the space to be cooled and subsequently rejects that heat elsewhere. Figure 1 depicts a typical, single-stage vapor-compression system. All such systems have four components: a compressor, a condenser,


id: vapor-compression-refrigeration-20260505-1
file: data/en.wikipedia.org/wiki/Vapor-compression_refrigeration-1.md
category: reference
title: Vapor-compression refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor-compression_refrigeration
date_saved: 2026-05-05T10:51:25.495110+00:00
instance: kb-cron
parent: vapor-compression-refrigeration-20260505-0
summary:
The selection of working fluid has a significant impact on the performance of the refrigeration cycles and as such it plays a key role when it comes to designing or simply choosing an ideal machine for a certain task. One of the most widespread refrigerants is "Freon". Freon is a trade name for a family of haloalkane refrigerants manufactured by DuPont and other companies. These refrigerants were commonly used due to their superior stability and safety properties: they were not flammable at room temperature and atmospheric pressure, nor obviously toxic as were the fluids they replaced, such as sulfur dioxide. Haloalkanes are also an order(s) of magnitude more expensive than petroleum-derived flammable alkanes of similar or better cooling performance. Unfortunately, chlorine- and fluorine-bearing refrigerants reach the upper atmosphere when they escape. In the stratosphere, substances like CFCs and HCFCs break up due to UV radiation, releasing their chlorine free-radicals. These chlorine free-radicals act as catalysts in the breakdown of ozone through chain reactions. One CFC molecule can cause thousands of ozone molecules to break down. This causes severe damage to the ozone layer that shields the Earth's surface from the Sun's strong UV radiation and has been shown to lead


id: vapor-compression-refrigeration-20260505-2
file: data/en.wikipedia.org/wiki/Vapor-compression_refrigeration-2.md
category: reference
title: Vapor-compression refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor-compression_refrigeration
date_saved: 2026-05-05T10:51:25.495110+00:00
instance: kb-cron
parent: vapor-compression-refrigeration-20260505-0
summary:
Hermetic motor, hermetic compressor Hermetic motor, semi-hermetic compressor Open motor (belt driven or close coupled), hermetic compressor Open motor (belt driven or close coupled), semi-hermetic compressor Typically in hermetic, and most semi-hermetic compressors (sometimes known as accessible hermetic compressors), the compressor and motor driving the compressor are integrated, and operate within the refrigerant system. The motor is hermetic and is designed to operate, and be cooled by, the refrigerant being compressed. The obvious disadvantage of hermetic motor compressors is that the motor drive cannot be maintained in situ, and the entire compressor must be removed if a motor fails. A further disadvantage is that burnt out windings can contaminate whole refrigeration systems requiring the system to be entirely pumped down, and the refrigerant replaced. An open compressor has a motor drive which is outside of the refrigeration system, and provides drive to the compressor by means of an input shaft with suitable gland seals. Open compressor motors are typically air-cooled and can be fairly easily exchanged or repaired without degassing of the refrigeration system. The disadvantage of this type of compressor is a failure of the shaft seals, leading to loss of refrigerant. Open motor compressors are generally easier to


id: vapor-compression-refrigeration-20260505-3
file: data/en.wikipedia.org/wiki/Vapor-compression_refrigeration-3.md
category: reference
title: Vapor-compression refrigeration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor-compression_refrigeration
date_saved: 2026-05-05T10:51:25.495110+00:00
instance: kb-cron
parent: vapor-compression-refrigeration-20260505-0
summary:
A horizontal or vertical pressure vessel, equipped internally with a demister, between the evaporator and the compressor inlet to capture and remove any residual, entrained liquid in the refrigerant vapor because liquid may damage the compressor. Such vapor–liquid separators are most often referred to as "suction line accumulators". (In other industrial processes, they are called "compressor suction drums" or "knockout pots".) Large commercial or industrial refrigeration systems may have multiple expansion valves and multiple evaporators in order to refrigerate multiple enclosed spaces or rooms. In such systems, the condensed liquid refrigerant may be routed into a pressure vessel, called a receiver, from which liquid refrigerant is withdrawn and routed through multiple pipelines to the multiple expansion valves and evaporators. Filter Dryers, installed before the compressors to catch any moisture or contaminants in the system and thus protect the compressors from internal damage Some refrigeration units may have multiple stages which requires the use of multiple compressors in various arrangements. In most of the world, the cooling capacity of refrigeration systems is measured in watts. Common residential air conditioning units range in capacity from 3.5 to 18 kilowatt. In a few countries it is measured in "tons of refrigeration", with common


id: vapor-liquid-solid-method-20260505-0
file: data/en.wikipedia.org/wiki/Vapor–liquid–solid_method-0.md
category: reference
title: Vapor–liquid–solid method
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor–liquid–solid_method
date_saved: 2026-05-05T10:51:26.738874+00:00
instance: kb-cron
parent: vapor-liquid-solid-method-20260505-0
summary:
The vapor–liquid–solid method (VLS) is a mechanism for the growth of one-dimensional structures, such as nanowires, from chemical vapor deposition. The growth of a crystal through direct adsorption of a gas phase on to a solid surface is generally very slow. The VLS mechanism circumvents this by introducing a catalytic liquid alloy phase which can rapidly adsorb a vapor to supersaturation levels, and from which crystal growth can subsequently occur from nucleated seeds at the liquid–solid interface. The physical characteristics of nanowires grown in this manner depend, in a controllable way, upon the size and physical properties of the liquid alloy. == Historical background == The VLS mechanism was proposed in 1964 as an explanation for silicon whisker growth from the gas phase in the presence of a liquid gold droplet placed upon a silicon substrate. The explanation was motivated by the absence of axial screw dislocations in the whiskers (which in themselves are a growth mechanism), the requirement of the gold droplet for growth, and the presence of the droplet at the tip of the whisker during the entire growth process. == Introduction == The VLS mechanism is typically described in three stages: Preparation of a liquid alloy droplet


id: vapor-liquid-solid-method-20260505-1
file: data/en.wikipedia.org/wiki/Vapor–liquid–solid_method-1.md
category: reference
title: Vapor–liquid–solid method
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor–liquid–solid_method
date_saved: 2026-05-05T10:51:26.738874+00:00
instance: kb-cron
parent: vapor-liquid-solid-method-20260505-0
summary:
The materials system used, as well as the cleanliness of the vacuum system and therefore the amount of contamination and/or the presence of oxide layers at the droplet and wafer surface during the experiment, both greatly influence the absolute magnitude of the forces present at the droplet/surface interface and, in turn, determine the shape of the droplets. The shape of the droplet, i.e. the contact angle (β0, see Figure 4) can, be modeled mathematically, however, the actual forces present during growth are extremely difficult to measure experimentally. Nevertheless, the shape of a catalyst particle at the surface of a crystalline substrate is determined by a balance of the forces of surface tension and the liquid–solid interface tension. The radius of the droplet varies with the contact angle as: R = r o sin ⁡ ( β o ) , {\displaystyle R={\frac {r_{\mathrm {o} }}{\sin(\beta _{\mathrm {o} })}},} where r0 is the radius of the contact area and β0 is defined by a modified Young’s equation: σ 1 cos ⁡ ( β o ) = σ s − σ l s − τ r o {\displaystyle \sigma _{\mathrm {1} }\cos(\beta _{\mathrm {o} })=\sigma _{\mathrm {s} }-\sigma _{\mathrm {ls} }-{\frac {\tau }{r_{\mathrm


id: vapor-liquid-solid-method-20260505-2
file: data/en.wikipedia.org/wiki/Vapor–liquid–solid_method-2.md
category: reference
title: Vapor–liquid–solid method
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vapor–liquid–solid_method
date_saved: 2026-05-05T10:51:26.738874+00:00
instance: kb-cron
parent: vapor-liquid-solid-method-20260505-0
summary:
=== Thermal evaporation === Some very interesting nanowires microstructures can be obtained by simply thermally evaporating solid materials. This technique can be carried out in a relatively simple setup composed of a dual-zone vacuum furnace. The hot end of the furnace contains the evaporating source material, while the evaporated particles are carrier downstream, (by way of a carrier gas) to the colder end of the furnace where they can absorb, nucleate, and grow on a desired substrate. === Metal-catalyzed molecular beam epitaxy === Molecular beam epitaxy (MBE) has been used since 2000 to create high-quality semiconductor wires based on the VLS growth mechanism. However, in metal-catalyzed MBE the metal particles do not catalyze a reaction between precursors but rather adsorb vapor phase particles. This is because the chemical potential of the vapor can be drastically lowered by entering the liquid phase. MBE is carried out under ultra-high vacuum (UHV) conditions where the mean-free-path (distance between collisions) of source atoms or molecules is on the order of meters. Therefore, evaporated source atoms (from, say, an effusion cell) act as a beam of particles directed towards the substrate. The growth rate of the process is very slow, the deposition conditions are very


id: vaporization-20260505-0
file: data/en.wikipedia.org/wiki/Vaporization-0.md
category: reference
title: Vaporization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vaporization
date_saved: 2026-05-05T10:51:27.918605+00:00
instance: kb-cron
parent: vaporization-20260505-0
summary:
Vaporization (vapourisation in British English) of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon (a phenomenon in which the whole object or substance is involved in the process). == Evaporation == Evaporation is a phase transition from the liquid phase to vapor (a state of substance below critical temperature) that occurs at temperatures below the boiling temperature at a given pressure. Evaporation occurs on the surface. Evaporation only occurs when the partial pressure of vapor of a substance is less than the equilibrium vapor pressure. For example, due to constantly decreasing pressures, vapor pumped out of a solution will eventually leave behind a cryogenic liquid. == Boiling == Boiling is also a phase transition from the liquid phase to gas phase, but boiling is the formation of vapor as bubbles of vapor below the surface of the liquid. Boiling occurs when the equilibrium vapor pressure of the substance is greater than or equal to the atmospheric pressure. The temperature at which boiling occurs is the boiling temperature, or boiling point. The boiling point varies


id: verneuil-method-20260505-0
file: data/en.wikipedia.org/wiki/Verneuil_method-0.md
category: reference
title: Verneuil method
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Verneuil_method
date_saved: 2026-05-05T10:51:29.108102+00:00
instance: kb-cron
parent: verneuil-method-20260505-0
summary:
The Verneuil method (or Verneuil process or Verneuil technique), also called flame fusion, was the first commercially successful method of manufacturing synthetic gemstones, developed in late 1883 by the French chemist Auguste Verneuil. It is primarily used to produce the ruby, sapphire and padparadscha varieties of corundum, as well as the diamond simulants rutile, strontium titanate and spinel. The principle of the process involves melting a finely powdered substance using an oxyhydrogen flame, and crystallising the melted droplets into a boule. The process is considered to be the founding step of modern industrial crystal growth technology, and remains in wide use to this day. == History == Since the study of alchemy began, there have been attempts to synthetically produce precious stones, and ruby, being one of the prized cardinal gems, has long been a prime candidate. In the 19th century, significant advances were achieved, with the first ruby formed by melting two smaller rubies together in 1817, and the first microscopic crystals created from alumina (aluminium oxide) in a laboratory in 1837. By 1877, chemist Edmond Frémy had devised an effective method for commercial ruby manufacture by using molten baths of alumina, yielding the first gemstone-quality synthetic stones. The


id: verneuil-method-20260505-1
file: data/en.wikipedia.org/wiki/Verneuil_method-1.md
category: reference
title: Verneuil method
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Verneuil_method
date_saved: 2026-05-05T10:51:29.108102+00:00
instance: kb-cron
parent: verneuil-method-20260505-0
summary:
One of the most crucial factors in successfully crystallising an artificial gemstone is obtaining highly pure starting material, with at least 99.9995% purity. In the case of manufacturing rubies, sapphires or padparadscha, this material is alumina. The presence of sodium impurities is especially undesirable, as it makes the crystal opaque. But because the bauxite from which alumina is obtained is most likely by way of the Bayer process (the first stage of which introduces caustic soda in order to separate the Al2O3) particular attention must be paid to the feedstock. Depending on the desired colouration of the crystal, small quantities of various oxides are added, such as chromium oxide for a red ruby, or ferric oxide and titania for a blue sapphire. Other starting materials include titania for producing rutile, or titanyl double oxalate for producing strontium titanate. Alternatively, small, valueless crystals of the desired product can be used. This starting material is finely powdered, and placed in a container within a Verneuil furnace, with an opening at the bottom through which the powder can escape when the container is vibrated. While the powder is being released, oxygen is supplied into the furnace, and travels with the powder down a


id: vinyloop-20260505-0
file: data/en.wikipedia.org/wiki/VinyLoop-0.md
category: reference
title: VinyLoop
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/VinyLoop
date_saved: 2026-05-05T10:51:30.349993+00:00
instance: kb-cron
parent: vinyloop-20260505-0
summary:
VinyLoop is a proprietary physical plastic recycling process for polyvinyl chloride (PVC). It is based on dissolution in order to separate PVC from other materials or impurities. == Background == A major factor of the recycling of polyvinyl chloride waste is the purity of the recycled material. In most composite materials, PVC is among several other materials, such as wood, metal, or textile. To make new products from the recycled PVC, it is necessary to separate it from other materials. Traditional recycling methods are not sufficient and expensive because this separation has to be done manually and product by product. VinyLoop is a recycling process which separates PVC from other materials through a process of dissolution, filtration and separation of contamination. A solvent is used in a closed loop to elute PVC from the waste. This makes it possible to recycle composite structure PVC waste, which would normally be incinerated or put in a landfill site. == Process == The process consists of the following steps: Pre-treatment: waste plastics are cleaned, ground and mixed Dissolution: a specific solvent is used to selectively dissolve the PVC compound in a closed loop Filtration: impurities which have not been dissolved are removed through


id: visbreaker-20260505-0
file: data/en.wikipedia.org/wiki/Visbreaker-0.md
category: reference
title: Visbreaker
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Visbreaker
date_saved: 2026-05-05T10:51:31.523020+00:00
instance: kb-cron
parent: visbreaker-20260505-0
summary:
A visbreaker is a processing unit in an oil refinery whose purpose is to minimize the quantity of residual oil produced in the distillation of crude oil and to increase the yield of more valuable middle distillates (heating oil and diesel) by the refinery. A visbreaker thermally cracks large hydrocarbon molecules in the oil by heating in a furnace to lower its viscosity and to produce small quantities of light hydrocarbons. (LPG and gasoline). The process name of "visbreaker" refers to the fact that the process lowers (i.e., breaks) the viscosity of the residual oil. The process is non-catalytic. == Process objectives == The objectives of visbreaking are: Lower the viscosity of the feed stream: Typically this is the residue from vacuum distillation of crude oil but can also be the residue from hydroskimming operations, natural bitumen from seeps in the ground or tar sands, and even certain high viscosity crude oils. Lower the amount of residual fuel oil produced by a refinery: Residual fuel oil is generally regarded as a low value product. Demand for residual fuel continues to decrease as it is replaced in its traditional markets, such as fuel needed to generate steam in power stations, by


id: visbreaker-20260505-1
file: data/en.wikipedia.org/wiki/Visbreaker-1.md
category: reference
title: Visbreaker
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Visbreaker
date_saved: 2026-05-05T10:51:31.523020+00:00
instance: kb-cron
parent: visbreaker-20260505-0
summary:
=== Fuel oil stability === The severity of visbreaker operation is normally limited by the need to produce a visbreaker tar that can be blended to make a stable fuel oil. Stability in this case is taken to mean the tendency of a fuel oil to produce sediments when stored. These sediments are undesirable as they can quickly foul the filters of pumps used to move the oil necessitating time-consuming maintenance. Vacuum residue fed to a visbreaker can be considered to be composed of the following: Asphaltenes: large polycyclic molecules that are suspended in the oil in a colloidal form Resins: also polycyclic but of a lower molecular weight than asphaltenes Aromatic hydrocarbons: derivatives of benzene, toluene and xylenes Parafinic hydrocarbons: alkanes Visbreaking preferentially cracks aliphatic compounds which have relatively low sulphur contents, low density and high viscosity and the effect of their removal can be clearly seen in the change in quality between feed and product. A too severe cracking in a visbreaker will lead to the asphaltene colloid becoming metastable. Subsequent addition of a diluent to manufacture a finished fuel oil can cause the colloid to break down, precipitating asphaltenes as a sludge. It has been observed that


id: vulcanization-20260505-0
file: data/en.wikipedia.org/wiki/Vulcanization-0.md
category: reference
title: Vulcanization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vulcanization
date_saved: 2026-05-05T10:51:32.658828+00:00
instance: kb-cron
parent: vulcanization-20260505-0
summary:
Vulcanization (British English: vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur and heat, which remains the most common practice. It has also grown to include the hardening of other (synthetic) rubbers via various means. Examples include silicone rubber via room temperature vulcanising and chloroprene rubber (neoprene) using metal oxides. Vulcanization can be defined as the curing of elastomers, with the terms 'vulcanization' and 'curing' sometimes used interchangeably in this context. It works by forming cross-links between sections of the polymer chain which results in increased rigidity and durability, as well as other changes in the mechanical and electrical properties of the material. Vulcanization, in common with the curing of other thermosetting polymers, is generally irreversible. The word was suggested by William Brockedon (a friend of Thomas Hancock who attained the British patent for the process) based on the god Vulcan who was associated with heat and sulfur in volcanoes. == History == In ancient Mesoamerican cultures, rubber was used to make balls, sandal soles, elastic bands, and waterproof containers. It was cured using sulfur-rich plant juices, an early form of vulcanization. In the 1830s, Charles Goodyear


id: water-gas-shift-reaction-20260505-0
file: data/en.wikipedia.org/wiki/Water–gas_shift_reaction-0.md
category: reference
title: Water–gas shift reaction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Water–gas_shift_reaction
date_saved: 2026-05-05T10:51:33.831884+00:00
instance: kb-cron
parent: water-gas-shift-reaction-20260505-0
summary:
The water–gas shift reaction (WGSR) describes the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen: CO + H2O ⇌ CO2 + H2 The water gas shift reaction was discovered by Italian physicist Felice Fontana in 1780. It was not until much later that the industrial value of this reaction was realized. Before the early 20th century, hydrogen was obtained by reacting steam under high pressure with iron to produce iron oxide and hydrogen. With the development of industrial processes that required hydrogen, such as the Haber–Bosch ammonia synthesis, a less expensive and more efficient method of hydrogen production was needed. As a resolution to this problem, the WGSR was combined with the gasification of coal to produce hydrogen. == Applications == The WGSR is a highly valuable industrial reaction that is used in the manufacture of ammonia, hydrocarbons, methanol, and hydrogen. Its most important application is in conjunction with the conversion of carbon monoxide from steam reforming of methane or other hydrocarbons in the production of hydrogen. In the Fischer–Tropsch process, the WGSR is one of the most important reactions used to balance the H2/CO ratio. It provides a source of hydrogen at the expense


id: water-gas-shift-reaction-20260505-1
file: data/en.wikipedia.org/wiki/Water–gas_shift_reaction-1.md
category: reference
title: Water–gas shift reaction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Water–gas_shift_reaction
date_saved: 2026-05-05T10:51:33.831884+00:00
instance: kb-cron
parent: water-gas-shift-reaction-20260505-0
summary:
Catalysts for the lower temperature WGS reaction are commonly based on copper or copper oxide loaded ceramic phases, While the most common supports include alumina or alumina with zinc oxide, other supports may include rare earth oxides, spinels or perovskites. A typical composition of a commercial LTS catalyst has been reported as 32-33% CuO, 34-53% ZnO, 15-33% Al2O3. The active catalytic species is CuO. The function of ZnO is to provide structural support as well as prevent the poisoning of copper by sulfur. The Al2O3 prevents dispersion and pellet shrinkage. The LTS shift reactor operates at a range of 200–250 °C. The upper temperature limit is due to the susceptibility of copper to thermal sintering. These lower temperatures also reduce the occurrence of side reactions that are observed in the case of the HTS. Noble metals such as platinum, supported on ceria, have also been used for LTS. == Mechanism == The WGSR has been extensively studied for over a hundred years. The kinetically relevant mechanism depends on the catalyst composition and the temperature. Two mechanisms have been proposed: an associative Langmuir–Hinshelwood mechanism and a redox mechanism. The redox mechanism is generally regarded as kinetically relevant during the high-temperature WGSR


id: weldon-process-20260505-0
file: data/en.wikipedia.org/wiki/Weldon_process-0.md
category: reference
title: Weldon process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Weldon_process
date_saved: 2026-05-05T10:51:35.011276+00:00
instance: kb-cron
parent: weldon-process-20260505-0
summary:
The Weldon process is a process developed in 1866 by Walter Weldon for recovering manganese dioxide for re-use in chlorine manufacture. Commercial operations started at the Gamble works in St. Helens in 1869. The process is described in considerable detail in the book, The Alkali Industry, by J.R. Partington,D.Sc. The common method to manufacture chlorine at the time, was to react manganese dioxide (and related oxides) with hydrochloric acid to give chlorine: MnO2 + 4 HCl → MnCl2 + Cl2 + 2H2O Weldon's contribution was to develop a process to recycle the manganese. The waste manganese(II) chloride solution is treated with lime, steam and oxygen, producing calcium manganite(IV): 2 MnCl2 + 3 Ca(OH)2 + O2 → CaO·2MnO2 + 3 H2O + 2 CaCl2 The resulting calcium manganite can be reacted with HCl as in related processes: CaO·2MnO2 + 10 HCl → CaCl2 + 2 MnCl2 + 2 Cl2 + 5 H2O The manganese(II) chloride can be recycled, while the calcium chloride is a waste byproduct. The Weldon process was first replaced by the Deacon process and later by the Chloralkali process. == References == == Further reading == "The Chlorine industry". Lenntech. Retrieved 11 September 2018. Lunge, Georg (1911). "Alkali


id: wellman-lord-process-20260505-0
file: data/en.wikipedia.org/wiki/Wellman–Lord_process-0.md
category: reference
title: Wellman–Lord process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wellman–Lord_process
date_saved: 2026-05-05T10:51:36.186543+00:00
instance: kb-cron
parent: wellman-lord-process-20260505-0
summary:
The Wellman–Lord process is a regenerable process to remove sulfur dioxide from flue gas (flue-gas desulfurization) without creating a throwaway sludge product. In this process, sulfur dioxide from flue gas is absorbed in a sodium sulfite solution in water forming sodium bisulfite; other components of flue gas are not absorbed. After lowering the temperature the bisulfite is converted to the sodium pyrosulfite which precipitates. Upon heating, the two previously described chemical reactions are reversed, and sodium pyrosulfite is converted to a concentrated stream of sulfur dioxide and sodium sulfite. The sulfur dioxide can be used for further reactions (e.g. the production of sulfuric acid), and the sulfite is reintroduced into the process. Na2SO3 + SO2 + H2O → 2NaHSO3 2NaHSO3 → Na2S2O5↓ + H2O Na2S2O5 + H2O → 2NaHSO3 2NaHSO3 → Na2SO3 + SO2 + H2O In its initial version (Crane Station, Maryland, 1968) the process was based on potassium sulfite, but the economic prognosis was poor. Interest in the process occurred because of the worldwide shortage of sulfur in 1967 and resulting high prices; power-plant flue gas was viewed as an additional source of sulfur to relieve the shortage. the later version used sodium sulfite and was installed (as


id: wet-oxidation-20260505-0
file: data/en.wikipedia.org/wiki/Wet_oxidation-0.md
category: reference
title: Wet oxidation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wet_oxidation
date_saved: 2026-05-05T10:51:37.356344+00:00
instance: kb-cron
parent: wet-oxidation-20260505-0
summary:
Wet oxidation is a form of hydrothermal treatment. It is the oxidation of dissolved or suspended components in water using oxygen as the oxidizer. It is referred to as wet air oxidation (WAO) when air is used. The oxidation reactions occur in superheated water at a temperature above the normal boiling point of water (100 °C), but below the critical point (374 °C). The system must be maintained under pressure to avoid excessive evaporation of water. This is done to control energy consumption due to the latent heat of vaporization. It is also done because liquid water is necessary for most of the oxidation reactions to occur. Compounds oxidize under wet oxidation conditions that would not oxidize under dry conditions at the same temperature and pressure. Wet oxidation has been used commercially for around 60 years. It is used predominantly for treating wastewater. It is often referred to as Zimpro (from ZIMmerman PROcess), after Fred J. Zimmermann who commercialized it in the mid 20th century. == System Description == Commercial systems typically use a bubble column reactor, where air is bubbled through a vertical column that is liquid full of the hot and pressurized wastewater. Fresh wastewater enters the bottom


id: ziegler-process-20260505-0
file: data/en.wikipedia.org/wiki/Ziegler_process-0.md
category: reference
title: Ziegler process
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ziegler_process
date_saved: 2026-05-05T10:51:38.572294+00:00
instance: kb-cron
parent: ziegler-process-20260505-0
summary:
In organic chemistry, the Ziegler process (also called the Ziegler-Alfol synthesis) is a method for producing fatty alcohols from ethylene using an organoaluminium compound. The reaction produces linear primary alcohols with an even numbered carbon chain. The process uses an aluminum compound to oligomerize ethylene and allow the resulting alkyl group to be oxygenated. The usually targeted products are fatty alcohols, which are otherwise derived from natural fats and oils. Fatty alcohols are used in food and chemical processing. They are useful due to their amphipathic nature. The synthesis route is named after Karl Ziegler, who described the process in 1955. == Process details == The Ziegler alcohol synthesis involves oligomerization of ethylene using triethylaluminium followed by oxidation. The triethylaluminium is produced by action of aluminium, ethylene, and hydrogen gas. In the production process, two-thirds of the triethylaluminium produced is recycled back into the reactor, and only one-third is used to produce the fatty alcohols. The recycling step is used to produce triethylaluminium at a higher yield and with less time. Triethylaluminium reacts with ethylene to form higher molecular weight trialkylaluminium. The number of equivalents of ethylene n equals the total number of monomer units being grown on the initial


id: chemical-property-20260505-0
file: data/en.wikipedia.org/wiki/Chemical_property-0.md
category: reference
title: Chemical property
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemical_property
date_saved: 2026-05-05T10:51:40.083916+00:00
instance: kb-cron
parent: chemical-property-20260505-0
summary:
A chemical property is any of a material's properties that becomes evident during, or after, a chemical reaction; that is, any attribute that can be established only by changing a substance's chemical identity. Simply speaking, chemical properties cannot be determined just by viewing or touching the substance; the substance's internal structure must be affected greatly for its chemical properties to be investigated. When a substance goes under a chemical reaction, the properties will change drastically, resulting in chemical change. However, a catalytic property would also be a chemical property. Chemical properties can be contrasted with physical properties, which can be discerned without changing the substance's structure. However, for many properties within the scope of physical chemistry, and other disciplines at the boundary between chemistry and physics, the distinction may be a matter of researcher's perspective. Material properties, both physical and chemical, can be viewed as supervenient; i.e., secondary to the underlying reality. Several layers of superveniency are possible. Chemical properties can be used for building chemical classifications. They can also be useful to identify an unknown substance or to separate or purify it from other substances. Materials science will normally consider the chemical properties of a substance to guide its


id: absolute-molar-mass-20260505-0
file: data/en.wikipedia.org/wiki/Absolute_molar_mass-0.md
category: reference
title: Absolute molar mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Absolute_molar_mass
date_saved: 2026-05-05T10:51:41.203455+00:00
instance: kb-cron
parent: absolute-molar-mass-20260505-0
summary:
Absolute molar mass is a process used to determine the characteristics of molecules. == History == The first absolute measurements of molecular weights (i.e. made without reference to standards) were based on fundamental physical characteristics and their relation to the molar mass. The most useful of these were membrane osmometry and sedimentation. Another absolute instrumental approach was also possible with the development of light scattering theory by Albert Einstein, Chandrasekhara Venkata Raman, Peter Debye, Bruno H. Zimm, and others. The problem with measurements made using membrane osmometry and sedimentation was that they only characterized the bulk properties of the polymer sample. Moreover, the measurements were excessively time consuming and prone to operator error. In order to gain information about a polydisperse mixture of molar masses, a method for separating the different sizes was developed. This was achieved by the advent of size exclusion chromatography (SEC). SEC is based on the fact that the pores in the packing material of chromatography columns could be made small enough for molecules to become temporarily lodged in their interstitial spaces. As the sample makes its way through a column the smaller molecules spend more time traveling in these void spaces than the larger ones,


id: absolute-molar-mass-20260505-1
file: data/en.wikipedia.org/wiki/Absolute_molar_mass-1.md
category: reference
title: Absolute molar mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Absolute_molar_mass
date_saved: 2026-05-05T10:51:41.203455+00:00
instance: kb-cron
parent: absolute-molar-mass-20260505-0
summary:
== Applications == Light scattering measurements can be applied to synthetic polymers, proteins, pharmaceuticals and particles such as liposomes, micelles, and encapsulated proteins. Measurements can be made in one of two modes which are un-fractionated (batch mode) or in continuous flow mode (with SEC, HPLC or any other flow fractionation method). Batch mode experiments can be performed either by injecting a sample into a flow cell with a syringe or with the use of discrete vials. These measurements are most often used to measure timed events like antibody-antigen reactions or protein assembly. Batch mode measurements can also be used to determine the second virial coefficient (A2), a value that gives a measure of the likelihood of crystallization or aggregation in a given solvent. Continuous flow experiments can be used to study material eluting from virtually any source. More conventionally, the detectors are coupled to a variety of different chromatographic separation systems. The ability to determine the mass and size of the materials eluting then combines the advantage of the separation system with an absolute measurement of the mass and size of the species eluting. The addition of an SLS detector coupled downstream to a chromatographic system allows the utility of


id: acidity-function-20260505-0
file: data/en.wikipedia.org/wiki/Acidity_function-0.md
category: reference
title: Acidity function
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Acidity_function
date_saved: 2026-05-05T10:51:42.360272+00:00
instance: kb-cron
parent: acidity-function-20260505-0
summary:
An acidity function is a measure of the acidity of a medium or solvent system, usually expressed in terms of its ability to donate protons to (or accept protons from) a solute (Brønsted acidity). The pH scale is by far the most commonly used acidity function, and is ideal for dilute aqueous solutions. Other acidity functions have been proposed for different environments, most notably the Hammett acidity function, H0, for superacid media and its modified version H− for superbasic media. The term acidity function is also used for measurements made on basic systems, and the term basicity function is uncommon. Hammett-type acidity functions are defined in terms of a buffered medium containing a weak base B and its conjugate acid BH+: H 0 = p K a + log ⁡ c B c B H + {\displaystyle H_{0}={\rm {p}}K_{\rm {a}}+\log {{c_{\rm {B}}} \over {c_{\rm {BH^{+}}}}}} where pKa is the dissociation constant of BH+. They were originally measured by using nitroanilines as weak bases or acid-base indicators and by measuring the concentrations of the protonated and unprotonated forms with UV-visible spectroscopy. Other spectroscopic methods, such as NMR, may also be used. The function H− is defined similarly for strong bases: H


id: adhesion-20260505-0
file: data/en.wikipedia.org/wiki/Adhesion-0.md
category: reference
title: Adhesion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adhesion
date_saved: 2026-05-05T10:51:43.594074+00:00
instance: kb-cron
parent: adhesion-20260505-0
summary:
Adhesion is the tendency of dissimilar particles or surfaces to cling to one another. (Cohesion refers to the tendency of similar or identical particles and surfaces to cling to one another.) The forces that cause adhesion and cohesion can be divided into several types. The intermolecular forces responsible for the function of various kinds of stickers and sticky tape fall into the categories of chemical adhesion, dispersive adhesion, and diffusive adhesion. In addition to the cumulative magnitudes of these intermolecular forces, there are also certain emergent mechanical effects. == Surface energy == Surface energy is conventionally defined as the work that is required to build an area of a particular surface. Another way to view the surface energy is to relate it to the work required to cleave a bulk sample, creating two surfaces. If the new surfaces are identical, the surface energy γ of each surface is equal to half the work of cleavage, W: γ = (1/2)W11. If the surfaces are unequal, the Young-Dupré equation applies: W12 = γ1 + γ2 – γ12, where γ1 and γ2 are the surface energies of the two new surfaces, and γ12 is the interfacial energy. This methodology can also be used


id: adhesion-20260505-1
file: data/en.wikipedia.org/wiki/Adhesion-1.md
category: reference
title: Adhesion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adhesion
date_saved: 2026-05-05T10:51:43.594074+00:00
instance: kb-cron
parent: adhesion-20260505-0
summary:
In surface science, the term adhesion almost always refers to dispersive adhesion. In a typical solid-liquid-gas system (such as a drop of liquid on a solid surrounded by air) the contact angle is used to evaluate adhesiveness indirectly, while a Centrifugal Adhesion Balance allows for direct quantitative adhesion measurements. Generally, cases where the contact angle is low are considered of higher adhesion per unit area. This approach assumes that the lower contact angle corresponds to a higher surface energy. Theoretically, the more exact relation between contact angle and work of adhesion is more involved and is given by the Young-Dupre equation. The contact angle of the three-phase system is a function not only of dispersive adhesion (interaction between the molecules in the liquid and the molecules in the solid) but also cohesion (interaction between the liquid molecules themselves). Strong adhesion and weak cohesion results in a high degree of wetting, a lyophilic condition with low measured contact angles. Conversely, weak adhesion and strong cohesion results in lyophobic conditions with high measured contact angles and poor wetting. London dispersion forces are particularly useful for the function of adhesive devices, because they do not require either surface to have any permanent polarity.


id: adhesion-20260505-2
file: data/en.wikipedia.org/wiki/Adhesion-2.md
category: reference
title: Adhesion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adhesion
date_saved: 2026-05-05T10:51:43.594074+00:00
instance: kb-cron
parent: adhesion-20260505-0
summary:
=== Diffusive === Some materials may merge at the joint by diffusion. This may occur when the molecules of both materials are mobile and soluble in each other. This would be particularly effective with polymer chains where one end of the molecule diffuses into the other material. It is also the mechanism involved in sintering. When metal or ceramic powders are pressed together and heated, atoms diffuse from one particle to the next. This joins the particles into one. Diffusive forces are somewhat like mechanical tethering at the molecular level. Diffusive bonding occurs when species from one surface penetrate into an adjacent surface while still being bound to the phase of their surface of origin. One instructive example is that of polymer-on-polymer surfaces. Diffusive bonding in polymer-on-polymer surfaces is the result of sections of polymer chains from one surface interdigitating with those of an adjacent surface. The freedom of movement of the polymers has a strong effect on their ability to interdigitate, and hence, on diffusive bonding. For example, cross-linked polymers are less capable of diffusion and interdigitation because they are bonded together at many points of contact, and are not free to twist into the adjacent surface. Uncrosslinked polymers


id: adhesion-20260505-3
file: data/en.wikipedia.org/wiki/Adhesion-3.md
category: reference
title: Adhesion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Adhesion
date_saved: 2026-05-05T10:51:43.594074+00:00
instance: kb-cron
parent: adhesion-20260505-0
summary:
=== Hysteresis === Hysteresis, in this case, refers to the restructuring of the adhesive interface over some period of time, with the result being that the work needed to separate two surfaces is greater than the work that was gained by bringing them together (W > γ1 + γ2). For the most part, this is a phenomenon associated with diffusive bonding. The more time is given for a pair of surfaces exhibiting diffusive bonding to restructure, the more diffusion will occur, the stronger the adhesion will become. The aforementioned reaction of certain polymer-on-polymer surfaces to ultraviolet radiation and oxygen gas is an instance of hysteresis, but it will also happen over time without those factors. In addition to being able to observe hysteresis by determining if W > γ1 + γ2 is true, one can also find evidence of it by performing "stop-start" measurements. In these experiments, two surfaces slide against one another continuously and occasionally stopped for some measured amount of time. Results from experiments on polymer-on-polymer surfaces show that if the stopping time is short enough, resumption of smooth sliding is easy. If, however, the stopping time exceeds some limit, there is an initial increase of resistance to


id: air-sensitivity-20260505-0
file: data/en.wikipedia.org/wiki/Air_sensitivity-0.md
category: reference
title: Air sensitivity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Air_sensitivity
date_saved: 2026-05-05T10:51:44.771119+00:00
instance: kb-cron
parent: air-sensitivity-20260505-0
summary:
Air sensitivity is a term used, particularly in chemistry, to denote the reactivity of chemical compounds with some constituent of air. Most often, reactions occur with atmospheric oxygen (O2) or water vapor (H2O), although reactions with the other constituents of air such as carbon monoxide (CO), carbon dioxide (CO2), and nitrogen (N2) are also possible. == Method == A variety of air-free techniques have been developed to handle air-sensitive compounds. Two main types of equipment are gloveboxes and Schlenk lines. Glove boxes are sealed cabinets filled with an inert gas such as argon or nitrogen. Normal laboratory equipment can be set up in the glovebox, and manipulated by the use of gloves that penetrate its walls. The atmosphere can be regulated to approximately atmospheric pressure and set to be pure nitrogen or other gas with which the chemicals will not react. Chemicals and equipment can be transferred in and out via an airlock. A Schlenk line is a vacuum and inert-gas dual-manifold that allows glassware to be evacuated and refilled with inert gas specially developed to work with air sensitive compounds. It is connected with a cold trap to prevent vapors from contaminating a rotary vane pump. The technique is


id: amphiphile-20260505-0
file: data/en.wikipedia.org/wiki/Amphiphile-0.md
category: reference
title: Amphiphile
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amphiphile
date_saved: 2026-05-05T10:51:45.967923+00:00
instance: kb-cron
parent: amphiphile-20260505-0
summary:
In chemistry, an amphiphile (from Greek αμφις (amphis) 'both' and φιλíα (philia) 'love, friendship'), also referred to as an amphipath, is a dipolar chemical compound possessing both hydrophilic (water-loving, polar) and lipophilic (fat-loving, nonpolar) properties within the same molecule. Such compound is called amphiphilic or amphipathic. This dipolar characteristic implies the existence of different chemical groups forming spatially segregated regions with contrasting surface polarity. Amphiphilic compounds include surfactants, detergents, block copolymers, and Janus particles. In aqueous solutions, amphiphiles are able to self-assemble to form a wide range of supramolecular structures, including micelles, lamellae, nanofibers, and biological membranes. Phospholipid amphiphiles constitute a significant class of biological amphiphiles composed of a polar-phosphate based head group and two hydrophobic fatty acid chains. Phospholipid bilayers are the major structural component of cell membranes, and serve as the basis for a number of research areas including chemistry and biochemistry, notably that of lipid polymorphism. Organic compounds containing hydrophilic groups at both ends of the molecule are called bolaamphiphiles. They are distinguished from the conventional head-tail amphiphiles by the prolate geometry of the micelles they form in aggregation. == Structure == The lipophilic group is typically a large hydrocarbon moiety, such as a long chain of


id: amphoterism-20260505-0
file: data/en.wikipedia.org/wiki/Amphoterism-0.md
category: reference
title: Amphoterism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amphoterism
date_saved: 2026-05-05T10:51:47.144736+00:00
instance: kb-cron
parent: amphoterism-20260505-0
summary:
In chemistry, an amphoteric compound (from Greek amphoteros 'both') is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used. == Etymology and terminology == Amphoteric is derived from the Greek word amphoteroi (ἀμφότεροι) meaning "both". Related words in acid-base chemistry are amphichromatic and amphichroic, both describing substances such as acid-base indicators which give one colour on reaction with an acid and another colour on reaction with a base. === Amphiprotism === Amphiprotism is exhibited by compounds with both Brønsted acidic and basic properties. A prime example is H2O. Amphiprotic molecules can either donate or accept a proton (H+). Amino acids (and proteins) are amphiprotic molecules because of their amine (−NH2) and carboxylic acid (−COOH) groups. === Ampholytes === Ampholytes are zwitterions ‒ molecules or ions that contain both acidic and basic functional groups. Amino acids H2N−RCH−CO2H have both a basic group −NH2 and an acidic group −COOH. Often such species exists as several structures in chemical equilibrium: H2N−CRH−CO2H + H2O ⇌ H2N−CRH−COO− + H3O+ ⇌ H3N+−CRH−COOH + HO− ⇌ H3N+−CRH−COO− + H2O In approximately neutral aqueous solution (pH


id: amphoterism-20260505-1
file: data/en.wikipedia.org/wiki/Amphoterism-1.md
category: reference
title: Amphoterism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Amphoterism
date_saved: 2026-05-05T10:51:47.144736+00:00
instance: kb-cron
parent: amphoterism-20260505-0
summary:
SnO 2 + 4 HCl acid ↽ − − ⇀ SnCl 4 + 2 H 2 O {\displaystyle {\ce {SnO2 + {\overset {acid}{4 HCl}}<=> SnCl4 + 2H2O}}} SnO 2 + 4 NaOH base + 2 H 2 O ↽ − − ⇀ Na 4 [ Sn ( OH ) 8 ] {\displaystyle {\ce {SnO2 + {\overset {base}{4 NaOH}}+ 2H2O <=> Na4[Sn(OH)8]}}} Vanadium dioxide (VO2): VO 2 + 2 HCl acid ⟶ VOCl 2 + H 2 O {\displaystyle {\ce {VO2 + {\overset {acid}{2 HCl}}-> VOCl2 + H2O}}} 4 VO 2 + 2 NaOH base ⟶ Na 2 V 4 O 9 + H 2 O {\displaystyle {\ce {4 VO2 + {\overset {base}{2 NaOH}}-> Na2V4O9 + H2O}}} Some other elements which form amphoteric oxides are gallium, indium, scandium, titanium, zirconium, chromium, iron, cobalt, copper, silver, gold, germanium, antimony, bismuth, beryllium, and tellurium. == Hydroxides == Aluminium hydroxide is also amphoteric: Al ( OH ) 3 + 3 HCl acid ⟶ AlCl 3 + 3 H 2 O {\displaystyle {\ce {Al(OH)3 + {\overset {acid}{3 HCl}}-> AlCl3 + 3 H2O}}} Al ( OH ) 3 + NaOH base ⟶ Na [ Al ( OH ) 4 ] {\displaystyle {\ce {Al(OH)3 + {\overset {base}{NaOH}}->


id: anhydrous-20260505-0
file: data/en.wikipedia.org/wiki/Anhydrous-0.md
category: reference
title: Anhydrous
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Anhydrous
date_saved: 2026-05-05T10:51:48.344148+00:00
instance: kb-cron
parent: anhydrous-20260505-0
summary:
A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achieve perfect dryness; anhydrous compounds gradually absorb water from the atmosphere so they must be stored carefully. Substances that contain water or its constituent elements are called hydrates. == Solids == Many salts and solids can be dried using heat, or under vacuum. Desiccators can also be used to store reagents in dry conditions. Common desiccants include phosphorus pentoxide and silica gel. Chemists may also require dry glassware for sensitive reactions. This can be achieved by drying glassware in an oven, by flame, or under vacuum. Dry solids can be produced by freeze-drying, which is also known as lyophilization. == Liquids or solvents == In many cases, the presence of water can prevent a reaction from happening, or cause undesirable products to form. To prevent this, anhydrous solvents must be used when performing certain reactions. Examples of reactions requiring the use of anhydrous solvents are the Grignard reaction and the Wurtz reaction. Solvents have typically been dried using distillation or


id: aniline-point-20260505-0
file: data/en.wikipedia.org/wiki/Aniline_point-0.md
category: reference
title: Aniline point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Aniline_point
date_saved: 2026-05-05T10:51:49.519730+00:00
instance: kb-cron
parent: aniline-point-20260505-0
summary:
The aniline point of an oil is defined as the minimum temperature at which equal volumes of aniline (C6H5NH2) and lubricant oil are miscible, i.e. form a single phase upon mixing. The value gives an approximation for the content of aromatic compounds in the oil, since the miscibility of aniline, which is also an aromatic compound suggests the presence of similar (i.e. aromatic) compounds in the oil. The lower the aniline point, the greater is the content of aromatic compounds in the oil. The aniline point serves as a reasonable proxy for aromaticity of oils consisting mostly of saturated hydrocarbons (i.e. alkanes, paraffins) or unsaturated compounds (mostly aromatics). Significant chemical functionalization of the oil (chlorination, sulfonation, etc.) can interfere with the measurement, due to changes to the solvency of the functionalized oil. Aniline point indicates if an oil is likely to damage elastomers (rubber compounds) that come in contact with the oil. == Determination of aniline point == Equal volumes of aniline and oil are stirred continuously in a test tube and heated until the two merge into a homogeneous solution. Heating is stopped and the tube is allowed to cool. The temperature at which the two phases separate out


id: apicophilicity-20260505-0
file: data/en.wikipedia.org/wiki/Apicophilicity-0.md
category: reference
title: Apicophilicity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Apicophilicity
date_saved: 2026-05-05T10:51:50.695005+00:00
instance: kb-cron
parent: apicophilicity-20260505-0
summary:
Apicophilicity is the phenomenon in which electronegative substituents of trigonal bipyramidal pentacoordinate compounds prefer to occupy apical (axial) positions (Lap). The term "apicophilicity" was first proposed by Earl L. Muetterties in 1963 for the structural analysis of pentacoordinate phosphorus fluorides by 19F NMR. Since the apical bonding of a pentacoordinate typical (group 1, 2, 13-18) element compound consists of a 3-center-4-electron bond, in which the electron density is localized on two apical substituents, an arrangement in which electronegative substituents occupy apical positions is more stable. The apicophilicity of a substituent is defined as the difference in energy between two isomeric structures in which the substituent occupies an apical position and an equatorial position (Leq). Experimentally, instead of direct measurement of the energy difference, which is usually difficult to measure, the relative energy barriers for pseudorotation of isomers are used for determination of the apicophilicity scale. Some experimental and theoretical studies have been made to measure relative apicophilicities for various substituents. The apicophilicity of a substituent mainly depends on its electronegativity, but some other factors can also have an effect. A bulky substituent prefers equatorial positions, which are more distant from other substituents. A substituent with π-bonding ability also prefers equatorial


id: aqueous-solution-20260505-0
file: data/en.wikipedia.org/wiki/Aqueous_solution-0.md
category: reference
title: Aqueous solution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Aqueous_solution
date_saved: 2026-05-05T10:51:51.879940+00:00
instance: kb-cron
parent: aqueous-solution-20260505-0
summary:
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, also known as sodium chloride (NaCl), in water would be represented as Na+(aq) + Cl−(aq). The word aqueous (which comes from aqua) means pertaining to, related to, similar to, or dissolved in, water. As water is an excellent solvent and is also naturally abundant, it is a ubiquitous solvent in chemistry. Since water is frequently used as the solvent in experiments, the word solution refers to an aqueous solution, unless the solvent is specified. A non-aqueous solution is a solution in which the solvent is a liquid, but is not water. == Characteristics == Substances that are hydrophobic ('water-fearing') do not dissolve well in water, whereas those that are hydrophilic ('water-loving') do. An example of a hydrophilic substance is sodium chloride. In an aqueous solution the hydrogen ions (H+) and hydroxide ions (OH−) are in Arrhenius balance ([H+] [OH−] = Kw = 1 × 10−14 at 298 K). Acids and bases are aqueous solutions, as part of their Arrhenius definitions. An example of an Arrhenius acid


id: atomic-mass-20260505-0
file: data/en.wikipedia.org/wiki/Atomic_mass-0.md
category: reference
title: Atomic mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_mass
date_saved: 2026-05-05T10:51:53.116357+00:00
instance: kb-cron
parent: atomic-mass-20260505-0
summary:
Atomic mass (ma or m) is the mass of a single atom. The atomic mass mostly comes from the combined mass of the protons and neutrons in the nucleus, with minor contributions from the electrons and nuclear binding energy. The atomic mass of atoms, ions, or atomic nuclei is slightly less than the sum of the masses of their constituent protons, neutrons, and electrons, due to mass defect (explained by mass–energy equivalence: E = mc2). Atomic mass is often measured in dalton (Da) (a.k.a. unified atomic mass unit (u)). One dalton is equal to ⁠+1/12⁠ the mass of a carbon-12 atom in its natural state, given by the atomic mass constant mu = m(12C)/12 = 1 Da, where m(12C) is the atomic mass of carbon-12. Thus, the numerical value of the atomic mass of a nuclide when expressed in daltons is close to its mass number. The relative isotopic mass (see section below) can be obtained by dividing the atomic mass ma of an isotope by the atomic mass constant mu, yielding a dimensionless value. Thus, the atomic mass of a carbon-12 atom m(12C) is 12 Da by definition, but the relative isotopic mass of a carbon-12 atom Ar(12C) is


id: atomic-mass-20260505-1
file: data/en.wikipedia.org/wiki/Atomic_mass-1.md
category: reference
title: Atomic mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_mass
date_saved: 2026-05-05T10:51:53.116357+00:00
instance: kb-cron
parent: atomic-mass-20260505-0
summary:
protons and neutrons have different masses, and different nuclides have different ratios of protons and neutrons. atomic masses are reduced, by the binding energies between the protons and neutrons. The ratio of atomic mass to mass number (number of nucleons) varies from 0.9988381346(51) for 56Fe to 1.007825031898(14) for 1H. Any mass defect due to nuclear binding energy is experimentally a small fraction (less than 1%) of the mass of an equal number of free nucleons. When compared to the average mass per nucleon in carbon-12, which is moderately strongly bound compared with other atoms, the mass defect of binding for most atoms is an even smaller fraction of a dalton. Since free protons and neutrons differ from each other in mass by a small fraction of a dalton (1.38844933(49)×10−3 Da), rounding the relative isotopic mass, or the atomic mass of any given nuclide given in daltons to the nearest whole number, always gives the nucleon count, or mass number. Additionally, the neutron count (neutron number) may then be derived by subtracting the number of protons (atomic number) from the mass number (nucleon count). == Mass defect == The amount that the ratio of atomic masses to mass number deviates from


id: atomic-mass-20260505-2
file: data/en.wikipedia.org/wiki/Atomic_mass-2.md
category: reference
title: Atomic mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_mass
date_saved: 2026-05-05T10:51:53.116357+00:00
instance: kb-cron
parent: atomic-mass-20260505-0
summary:
The first scientists to determine relative atomic masses were John Dalton and Thomas Thomson between 1803 and 1805 and Jöns Jakob Berzelius between 1808 and 1826. Relative atomic mass (Atomic weight) was originally defined relative to that of the lightest element, hydrogen, which was taken as 1.00, and in the 1820s, Prout's hypothesis stated that atomic masses of all elements would prove to be exact multiples of that of hydrogen. Berzelius, however, soon proved that this was not even approximately true, and for some elements, such as chlorine, relative atomic mass, at about 35.5, falls almost exactly halfway between two integral multiples of that of hydrogen. Still later, this was shown to be largely due to a mix of isotopes, and that the atomic masses of pure isotopes, or nuclides, are multiples of the hydrogen mass, to within about 1%. In the 1860s, Stanislao Cannizzaro refined relative atomic masses by applying Avogadro's law (notably at the Karlsruhe Congress of 1860). He formulated a law to determine relative atomic masses of elements: the different quantities of the same element contained in different molecules are all whole multiples of the atomic weight and determined relative atomic masses and molecular masses by comparing


id: atomic-number-20260505-0
file: data/en.wikipedia.org/wiki/Atomic_number-0.md
category: reference
title: Atomic number
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_number
date_saved: 2026-05-05T10:51:54.272199+00:00
instance: kb-cron
parent: atomic-number-20260505-0
summary:
The atomic number or nuclear charge number (symbol Z, from the German Zahl, "number") of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (np) or the number of protons found in the nucleus of every atom of that element. The atomic number can be used to uniquely identify ordinary chemical elements. In an ordinary uncharged atom, the atomic number is also equal to the number of electrons. For an ordinary atom which contains protons, neutrons and electrons, the sum of the atomic number Z and the neutron number N gives the atom's atomic mass number A. Since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes) and the mass defect of the nucleon binding is always small compared to the nucleon mass, the atomic mass of any atom, when expressed in daltons (making a quantity called the "relative isotopic mass"), is within 1% of the whole number A. Atoms with the same atomic number but different neutron numbers, and hence different mass numbers, are known as isotopes. A little more than three-quarters


id: atomic-number-20260505-1
file: data/en.wikipedia.org/wiki/Atomic_number-1.md
category: reference
title: Atomic number
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_number
date_saved: 2026-05-05T10:51:54.272199+00:00
instance: kb-cron
parent: atomic-number-20260505-0
summary:
In 1911, Ernest Rutherford gave a model of the atom in which a central nucleus held most of the atom's mass and a positive charge which, in units of the electron's charge, was to be approximately equal to half of the atom's atomic weight, expressed in numbers of hydrogen atoms. This central charge would thus be approximately half the atomic weight (though it was almost 25% different from the atomic number of gold (Z = 79, A = 197), the single element from which Rutherford made his guess). Nevertheless, in spite of Rutherford's estimation that gold had a central charge of about 100 (but was element Z = 79 on the periodic table), a month after Rutherford's paper appeared, Antonius van den Broek first formally suggested that the central charge and number of electrons in an atom were exactly equal to its place in the periodic table (also known as element number, atomic number, and symbolized Z). This eventually proved to be the case. === Moseley's 1913 experiment === The experimental position improved dramatically after research by Henry Moseley in 1913. Moseley, after discussions with Bohr who was at the same lab (and who had used Van den Broek's hypothesis


id: atomic-number-20260505-2
file: data/en.wikipedia.org/wiki/Atomic_number-2.md
category: reference
title: Atomic number
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_number
date_saved: 2026-05-05T10:51:54.272199+00:00
instance: kb-cron
parent: atomic-number-20260505-0
summary:
== New elements == The quest for new elements is usually described using atomic numbers. As of 2026, all elements with atomic numbers 1 to 118 have been observed. The most recent element discovered was number 117 (tennessine) in 2009. Synthesis of new elements is accomplished by bombarding target atoms of heavy elements with ions, such that the sum of the atomic numbers of the target and ion elements equals the atomic number of the element being created. In general, the half-life of a nuclide becomes shorter as atomic number increases, though undiscovered nuclides with certain "magic" numbers of protons and neutrons may have relatively longer half-lives and comprise an island of stability. A hypothetical element composed only of neutrons, neutronium, has also been proposed and would have atomic number 0, but has never been observed. == See also == Atomic theory Chemical element – Chemical substance not composed of simpler ones Effective nuclear charge – Measurement in atomic physics Effective atomic number (compounds and mixtures) – Approximate atomic number calculated for materials with many elements Even and odd atomic nuclei – Nuclear physics classification method History of the periodic table – Development of the table of chemical elements List


id: relative-atomic-mass-20260505-0
file: data/en.wikipedia.org/wiki/Relative_atomic_mass-0.md
category: reference
title: Relative atomic mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Relative_atomic_mass
date_saved: 2026-05-05T10:51:55.504891+00:00
instance: kb-cron
parent: relative-atomic-mass-20260505-0
summary:
Relative atomic mass (symbol: Ar; sometimes abbreviated RAM or r.a.m.), also known by the deprecated synonym atomic weight, is a dimensionless physical quantity defined as the ratio of the average mass of atoms of a chemical element in a given sample to the atomic mass constant. The atomic mass constant (symbol: mu) is defined as being ⁠1/12⁠ of the mass of a carbon-12 atom. Since both quantities in the ratio are masses, the resulting value is dimensionless. These definitions remain valid even after the 2019 revision of the SI. For a single given sample, the relative atomic mass of a given element is the weighted arithmetic mean of the masses of the individual atoms (including all its isotopes) that are present in the sample. This quantity can vary significantly between samples because the sample's origin (and therefore its radioactive history or diffusion history) may have produced combinations of isotopic abundances in varying ratios. For example, due to a different mixture of stable carbon-12 and carbon-13 isotopes, a sample of elemental carbon from volcanic methane will have a different relative atomic mass than one collected from plant or animal tissues. The more common, and more specific quantity known as standard atomic


id: relative-atomic-mass-20260505-1
file: data/en.wikipedia.org/wiki/Relative_atomic_mass-1.md
category: reference
title: Relative atomic mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Relative_atomic_mass
date_saved: 2026-05-05T10:51:55.504891+00:00
instance: kb-cron
parent: relative-atomic-mass-20260505-0
summary:
== Other measures of the mass of atoms == Atomic mass (ma) is the mass of a single atom. It defines the mass of a specific isotope, which is an input value for the determination of the relative atomic mass. An example for three silicon isotopes is given below. A convenient unit of mass for atomic mass is the dalton (Da), which is also called the unified atomic mass unit (u). The relative isotopic mass is the ratio of the mass of a single atom to the atomic mass constant (mu = 1 Da). This ratio is dimensionless. == Determination of relative atomic mass == Modern relative atomic masses (a term specific to a given element sample) are calculated from measured values of atomic mass (for each nuclide) and isotopic composition of a sample. Highly accurate atomic masses are available for virtually all non-radioactive nuclides, but isotopic compositions are both harder to measure to high precision and more subject to variation between samples. For this reason, the relative atomic masses of the 22 mononuclidic elements (which are the same as the isotopic masses for each of the single naturally occurring nuclides of these elements) are known to especially high accuracy.


id: autoignition-temperature-20260505-0
file: data/en.wikipedia.org/wiki/Autoignition_temperature-0.md
category: reference
title: Autoignition temperature
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Autoignition_temperature
date_saved: 2026-05-05T10:51:56.728683+00:00
instance: kb-cron
parent: autoignition-temperature-20260505-0
summary:
The autoignition temperature (often called self-ignition temperature, spontaneous ignition temperature, minimum ignition temperature, or shortly ignition temperature, formerly also known as kindling point) of a substance is the lowest temperature at which it spontaneously ignites in a normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical ignites decreases as the pressure is decreased. Substances which spontaneously ignite in a normal atmosphere at naturally ambient temperatures are termed pyrophoric. Autoignition temperatures of liquid chemicals are typically measured using a 500-millilitre (18 imp fl oz; 17 US fl oz) flask placed in a temperature-controlled oven in accordance with the procedure described in ASTM E659. When measured for plastics, autoignition temperature can also be measured under elevated pressure and at 100% oxygen concentration. The resulting value is used as a predictor of viability for high-oxygen service. The main testing standard for this is ASTM G72. == Autoignition time equation == The time t ig {\displaystyle t_{\text{ig}}} it takes for a material to reach its autoignition temperature T ig {\displaystyle T_{\text{ig}}} when exposed to a heat flux q ″ {\displaystyle q''}


id: boiling-point-elevation-20260505-0
file: data/en.wikipedia.org/wiki/Boiling-point_elevation-0.md
category: reference
title: Boiling-point elevation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Boiling-point_elevation
date_saved: 2026-05-05T10:51:57.905771+00:00
instance: kb-cron
parent: boiling-point-elevation-20260505-0
summary:
Boiling-point elevation is the phenomenon whereby the boiling point of a liquid (a solvent) will be higher when another compound is added, meaning that a solution has a higher boiling point than a pure solvent. This happens whenever a non-volatile solute, such as a salt, is added to a pure solvent, such as water. The boiling point can be measured accurately using an ebullioscope. == Explanation == The boiling point elevation is a colligative property, which means that boiling point elevation is dependent on the number of dissolved particles but not their identity. It is an effect of the dilution of the solvent in the presence of a solute. It is a phenomenon that happens for all solutes in all solutions, even in ideal solutions, and does not depend on any specific solute–solvent interactions. The boiling point elevation happens both when the solute is an electrolyte, such as various salts, or a nonelectrolyte. In thermodynamic terms, the origin of the boiling point elevation is entropic and can be explained in terms of the vapor pressure or chemical potential of the solvent. In both cases, the explanation depends on the fact that many solutes are only present in the liquid phase


id: chaotropic-agent-20260505-0
file: data/en.wikipedia.org/wiki/Chaotropic_agent-0.md
category: reference
title: Chaotropic agent
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chaotropic_agent
date_saved: 2026-05-05T10:51:59.086420+00:00
instance: kb-cron
parent: chaotropic-agent-20260505-0
summary:
A chaotropic agent is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules (i.e. exerts chaotropic activity). This has an effect on the stability of the native state of other molecules in the solution, mainly macromolecules (proteins, nucleic acids) by weakening the hydrophobic effect. For example, a chaotropic agent reduces the amount of order in the structure of a protein formed by water molecules, both in the bulk and the hydration shells around hydrophobic amino acids, and may cause its denaturation. Conversely, an antichaotropic agent (kosmotropic) is a molecule in an aqueous solution that will increase the hydrophobic effects within the solution. Antichaotropic salts such as ammonium sulphate can be used to precipitate substances from the impure mixture. This is used in protein purification processes, to remove undesired proteins from solution. == Overview == A chaotropic agent is a substance which disrupts the structure of, and denatures, macromolecules such as proteins and nucleic acids (e.g. DNA and RNA). Chaotropic solutes increase the entropy of the system by interfering with intermolecular interactions mediated by non-covalent forces such as hydrogen bonds, van der Waals forces, and hydrophobic effects. Macromolecular structure and function is dependent on the


id: chemical-composition-20260505-0
file: data/en.wikipedia.org/wiki/Chemical_composition-0.md
category: reference
title: Chemical composition
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemical_composition
date_saved: 2026-05-05T10:52:00.270614+00:00
instance: kb-cron
parent: chemical-composition-20260505-0
summary:
A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds. Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for water is H2O: this means that each molecule of water is constituted by 2 atoms of hydrogen (H) and 1 atom of oxygen (O). The chemical composition of water may be interpreted as a 2:1 ratio of hydrogen atoms to oxygen atoms. Different types of chemical formulas are used to convey composition information, such as an empirical or molecular formula. Nomenclature can be used to express not only the elements present in a compound but their arrangement within the molecules of the compound. In this way, compounds will have unique names which can describe their elemental composition. == Composite mixture == The chemical composition of a mixture can be defined as the distribution of the individual substances that constitute the mixture, called "components". In other words, it is equivalent to quantifying the concentration of each component. Because there are different ways to define the concentration of a component, there are also different ways to


id: chemical-polarity-20260505-0
file: data/en.wikipedia.org/wiki/Chemical_polarity-0.md
category: reference
title: Chemical polarity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemical_polarity
date_saved: 2026-05-05T10:52:01.488345+00:00
instance: kb-cron
parent: chemical-polarity-20260505-0
summary:
In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end. Polar molecules must contain one or more polar bonds due to a difference in electronegativity between the bonded atoms. Molecules containing polar bonds have no molecular polarity if the bond dipoles cancel each other out by symmetry. Polar molecules interact through dipole-dipole intermolecular forces and hydrogen bonds. Polarity underlies a number of physical properties including surface tension, solubility, and melting and boiling points. == Polarity of bonds == Not all atoms attract electrons with the same force. The amount of "pull" an atom exerts on its electrons is called its electronegativity. Atoms with high electronegativities – such as fluorine, oxygen, and nitrogen – exert a greater pull on electrons than atoms with lower electronegativities such as alkali metals and alkaline earth metals. In a bond, this leads to unequal sharing of electrons between the atoms, as electrons will be drawn closer to the atom with the higher electronegativity. Because electrons have a negative charge, the unequal sharing of electrons within a bond leads to the formation of an


id: chemical-polarity-20260505-1
file: data/en.wikipedia.org/wiki/Chemical_polarity-1.md
category: reference
title: Chemical polarity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemical_polarity
date_saved: 2026-05-05T10:52:01.488345+00:00
instance: kb-cron
parent: chemical-polarity-20260505-0
summary:
A molecule is composed of one or more chemical bonds between molecular orbitals of different atoms. A molecule may be polar either as a result of polar bonds due to differences in electronegativity as described above, or as a result of an asymmetric arrangement of nonpolar covalent bonds and non-bonding pairs of electrons known as a full molecular orbital. While the molecules can be described as "polar covalent", "nonpolar covalent", or "ionic", this is often a relative term, with one molecule simply being more polar or more nonpolar than another. However, the following properties are typical of such molecules. === Boiling point === When comparing a polar and nonpolar molecule with similar molar masses, the polar molecule in general has a higher boiling point, because the dipole–dipole interaction between polar molecules results in stronger intermolecular attractions. One common form of polar interaction is the hydrogen bond, which is also known as the H-bond. For example, water forms H-bonds and has a molar mass M = 18 and a boiling point of +100 °C, compared to nonpolar methane with M = 16 and a boiling point of −161 °C. === Solubility === Due to the polar nature of the water molecule


id: chemical-polarity-20260505-2
file: data/en.wikipedia.org/wiki/Chemical_polarity-2.md
category: reference
title: Chemical polarity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemical_polarity
date_saved: 2026-05-05T10:52:01.488345+00:00
instance: kb-cron
parent: chemical-polarity-20260505-0
summary:
=== Amphiphilic molecules === Large molecules that have one end with polar groups attached and another end with nonpolar groups are described as amphiphiles or amphiphilic molecules. They are good surfactants and can aid in the formation of stable emulsions, or blends, of water and fats. Surfactants reduce the interfacial tension between oil and water by adsorbing at the liquid–liquid interface. == Predicting molecule polarity == Determining the point group is a useful way to predict polarity of a molecule. In general, a molecule will not possess dipole moment if the individual bond dipole moments of the molecule cancel each other out. This is because dipole moments are euclidean vector quantities with magnitude and direction, and a two equal vectors that oppose each other will cancel out. Any molecule with a centre of inversion ("i") or a horizontal mirror plane ("σh") will not possess dipole moments. Likewise, a molecule with more than one Cn axis of rotation will not possess a dipole moment because dipole moments cannot lie in more than one dimension. As a consequence of that constraint, all molecules with dihedral symmetry (Dn) will not have a dipole moment because, by definition, D point groups have two or


id: chemically-inert-20260505-0
file: data/en.wikipedia.org/wiki/Chemically_inert-0.md
category: reference
title: Chemically inert
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemically_inert
date_saved: 2026-05-05T10:52:02.654248+00:00
instance: kb-cron
parent: chemically-inert-20260505-0
summary:
In chemistry, the term chemically inert is used to describe a substance that is not chemically reactive. From a thermodynamic perspective, a substance is inert, or nonlabile, if it is thermodynamically unstable (negative standard Gibbs free energy of formation) yet decomposes at a slow, or negligible rate. Most of the noble gases, which appear in the last column of the periodic table, are classified as inert (or unreactive). These elements are stable in their naturally occurring form (gaseous form) and they are called inert gases. == Noble gas == The noble gases (helium, neon, argon, krypton, xenon, radon, and—in some cases—oganesson) were previously known as inert gases because of their perceived lack of chemical reactivity. This belief was invariably given credence by these elements possessing a complete valence electron shell and thus are disinclined from altering their current electron configuration per the octet 'rule'. It has now been experimentally shown under specific conditions that all of these gases, except oganesson, can react to form chemical compounds, such as xenon tetrafluoride. However, a large amount of energy is required to drive such reactions, usually in the form of heat, pressure, or radiation, often assisted by catalysts. == Inert gas == The


id: cloud-point-20260505-0
file: data/en.wikipedia.org/wiki/Cloud_point-0.md
category: reference
title: Cloud point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cloud_point
date_saved: 2026-05-05T10:52:03.828003+00:00
instance: kb-cron
parent: cloud-point-20260505-0
summary:
In liquids, the cloud point is the temperature below which a transparent solution undergoes either a liquid–liquid phase separation to form an emulsion or a liquid–solid phase transition to form either a stable sol or a suspension that settles as precipitate. The cloud point is analogous to the dew point at which a gas–liquid phase transition called condensation occurs in water vapour (humid air) to form liquid water (dew or clouds). When the temperature is below 0 °C, the dew point is called the frost point, as water vapour undergoes gas–solid phase transition called deposition, solidification, or freezing. In the petroleum industry, cloud point refers to the temperature below which paraffin wax in diesel or biowax in biodiesels forms a cloudy appearance. The presence of solidified waxes thickens the oil and clogs fuel filters and injectors in engines. The wax also accumulates on cold surfaces (producing, for example, pipeline or heat exchanger fouling) and forms an emulsion or sol with water. Therefore, cloud point indicates the tendency of the oil to plug filters or small orifices at cold operating temperatures. An everyday example of cloud point can be seen in olive oil stored in cold weather. Olive oil begins to


id: cold-filter-plugging-point-20260505-0
file: data/en.wikipedia.org/wiki/Cold_filter_plugging_point-0.md
category: reference
title: Cold filter plugging point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cold_filter_plugging_point
date_saved: 2026-05-05T10:52:04.997433+00:00
instance: kb-cron
parent: cold-filter-plugging-point-20260505-0
summary:
Cold filter plugging point (CFPP) is the lowest temperature, expressed in degrees Celsius (°C), at which a given volume of diesel type of fuel still passes through a standardized filtration device in a specified time when cooled under certain conditions. This test gives an estimate for the lowest temperature that a fuel will give trouble free flow in certain fuel systems. This is important as in cold temperate countries, a high cold filter plugging point will clog up vehicle engines more easily. The test is important in relation to the use of additives that allow spreading the usage of winter diesel at temperatures below the cloud point. The tests according to EN 590 show that a cloud point of +1 °C can have a CFPP −10 °C. Current additives allow a CFPP of −20 °C to be based on diesel fuel with a cloud point of −7 °C. The trustworthiness of the EN 590 have been criticized as being too low for modern diesel motors – the German ADAC has run a test series on customary winter diesel in a cold chamber. All diesel brands did exceed the legal minimum by 3 to 11 degrees in the laboratory according to


id: color-of-chemicals-20260505-0
file: data/en.wikipedia.org/wiki/Color_of_chemicals-0.md
category: reference
title: Color of chemicals
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Color_of_chemicals
date_saved: 2026-05-05T10:52:06.205084+00:00
instance: kb-cron
parent: color-of-chemicals-20260505-0
summary:
The color of chemicals is a physical property of chemicals that in most cases comes from the excitation of electrons due to an absorption of energy performed by the chemical. The study of chemical structure by means of energy absorption and release is generally referred to as spectroscopy. == Theory == All atoms and molecules are capable of absorbing and releasing energy in the form of photons, accompanied by a change of quantum state. The amount of energy absorbed or released is the difference between the energies of the two quantum states. There are various types of quantum state, including, for example, the rotational and vibrational states of a molecule. However the release of energy visible to the human eye, commonly referred to as visible light, spans the wavelengths approximately 380 nm to 760 nm, depending on the individual, and photons in this range usually accompany a change in atomic or molecular orbital quantum state. The perception of light is governed by three types of color receptors in the eye, which are sensitive to different ranges of wavelength within this band. The relationship between energy and wavelength is determined by the Planck-Einstein relation E = h f = h c


id: combustibility-and-flammability-20260505-0
file: data/en.wikipedia.org/wiki/Combustibility_and_flammability-0.md
category: reference
title: Combustibility and flammability
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Combustibility_and_flammability
date_saved: 2026-05-05T10:52:07.365620+00:00
instance: kb-cron
parent: combustibility-and-flammability-20260505-0
summary:
A combustible material is a material that can burn (i.e. sustain a flame) in air under certain conditions. A material is flammable if it ignites easily at room temperature. In other words, a combustible material takes more effort to ignite and a flammable material ignites almost immediately when exposed to a flame. The degree of flammability in air depends largely on how easy the material vaporizes. This is related to its composition-specific vapor pressure, which is temperature dependent. The quantity of vapor produced can be enhanced by increasing the surface area of the material, forming a mist or dust. Wood is an example. Finely divided wood dust can undergo explosive flames and produce a blast wave. A piece of paper (made from pulp) catches on fire quite easily. A heavy oak desk is much harder to ignite, even though the wood fibers are the same in all three materials. Common sense, and scientific consensus until the mid-1700s, suggests that material disappears when burned, as only the ash is left. Further scientific research has found that conservation of mass holds for chemical reactions. The burning of a solid material may appear to lose mass if the mass of combustion gases (such


id: combustibility-and-flammability-20260505-1
file: data/en.wikipedia.org/wiki/Combustibility_and_flammability-1.md
category: reference
title: Combustibility and flammability
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Combustibility_and_flammability
date_saved: 2026-05-05T10:52:07.365620+00:00
instance: kb-cron
parent: combustibility-and-flammability-20260505-0
summary:
=== Furniture flammability === Flammability of furniture is of concern as cigarettes and candle accidents can trigger domestic fires. In 1975, California began implementing Technical Bulletin 117 (TB 117), which required that materials such as polyurethane foam used to fill furniture be able to withstand a small open flame, equivalent to a candle, for at least 12 seconds. In polyurethane foam, furniture manufacturers typically meet TB 117 with additive halogenated organic flame retardants. No other U.S. states had similar standards. California had such a large market, manufacturers meet TB 117 in products that they distribute across the United States. The proliferation of flame retardants, especially halogenated organic flame retardants, in furniture across the United States is strongly linked to TB 117. When it became apparent that the risk-benefit ratio of this approach was unfavorable and the industry had used falsified documentation (i.e. see David Heimbach) for the use of flame retardants, California modified TB 117 to require that fabric covering upholstered furniture meet a smolder test that replaced the open flame test. Governor Jerry Brown signed the modified TB117-2013, which became effective in 2014. === Fabric flammability === Lightweight textiles with porous surfaces are the most flammable fabrics. Wool is


id: combustibility-and-flammability-20260505-2
file: data/en.wikipedia.org/wiki/Combustibility_and_flammability-2.md
category: reference
title: Combustibility and flammability
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Combustibility_and_flammability
date_saved: 2026-05-05T10:52:07.365620+00:00
instance: kb-cron
parent: combustibility-and-flammability-20260505-0
summary:
=== Flammability or explosive range === The lower flammability limit or lower explosive limit (LFL/LEL) represents the lowest air to fuel vapor concentration required for combustion to take place when ignited by an external source, for any chemical. Any concentration lower than this could not produce a flame or result in combustion. The upper flammability limit or upper explosive limit (UFL/UEL) represents the highest air to fuel vapor concentration at which combustion can take place when ignited by an external source. Any fuel-air mixture higher than this would be too concentrated to result in combustion. The values existing between these two limits represent the flammable or explosive range. Within this threshold, given an external ignition source, combustion of the particular fuel would likely happen. === Vapor pressure === The vapor pressure of a liquid is a measure of how much the vapor of the liquid tends to concentrate in the surrounding atmosphere as the liquid evaporates. Vapor pressure is a major determinant of the flash point and flame point, with higher vapor pressures leading to lower flash points and higher flammability ratings. == Codes == The International Code Council (ICC) developed fire code requirements to provide adequate protection to a


id: covalent-radius-20260505-0
file: data/en.wikipedia.org/wiki/Covalent_radius-0.md
category: reference
title: Covalent radius
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Covalent_radius
date_saved: 2026-05-05T10:52:09.662993+00:00
instance: kb-cron
parent: covalent-radius-20260505-0
summary:
The covalent radius, rcov, is a measure of the size of an atom that forms part of one covalent bond. It is usually measured either in picometres (pm) or angstroms (Å), with 1 Å = 100 pm. In principle, the sum of the two covalent radii should equal the covalent bond length between two atoms, R(AB) = r(A) + r(B). Moreover, different radii can be introduced for single, double and triple bonds (r1, r2 and r3 below), in a purely operational sense. These relationships are certainly not exact because the size of an atom is not constant but depends on its chemical environment. For heteroatomic A–B bonds, ionic terms may enter. Often the polar covalent bonds are shorter than would be expected based on the sum of covalent radii. Tabulated values of covalent radii are either average or idealized values, which nevertheless show a certain transferability between different situations, which makes them useful. The bond lengths R(AB) are measured by X-ray diffraction (more rarely, neutron diffraction on molecular crystals). Rotational spectroscopy can also give extremely accurate values of bond lengths. For homonuclear A–A bonds, Linus Pauling took the covalent radius to be half the single-bond length in the element, e.g.


id: critical-relative-humidity-20260505-0
file: data/en.wikipedia.org/wiki/Critical_relative_humidity-0.md
category: reference
title: Critical relative humidity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Critical_relative_humidity
date_saved: 2026-05-05T10:52:10.794935+00:00
instance: kb-cron
parent: critical-relative-humidity-20260505-0
summary:
The critical relative humidity (CRH) of a salt is defined as the relative humidity of the surrounding atmosphere (at a certain temperature) at which the material begins to absorb moisture from the atmosphere and below which it will not absorb atmospheric moisture. When the humidity of the atmosphere is equal to (or is greater than) the critical relative humidity of a sample of salt, the sample will take up water until all of the salt is dissolved to yield a saturated solution. All water-soluble salts and mixtures have characteristic critical humidities; it is a unique material property. The critical relative humidity of most salts decreases with increasing temperature. For instance, the critical relative humidity of ammonium nitrate decreases 22% with a temperature from 0 °C to 40 °C (32 °F to 104 °F). The critical relative humidity of several fertilizer salts is given in table 1: Table 1: Critical relative humidities of pure salts at 30°C. Mixtures of salts usually have lower critical humidities than either of the constituents. Fertilizers that contain Urea as an ingredient usually exhibit a much lower Critical Relative Humidity than Fertilizers without Urea. Table 2 shows CRH data for two-component mixtures: Table 2: Critical relative


id: crystal-structure-20260505-0
file: data/en.wikipedia.org/wiki/Crystal_structure-0.md
category: reference
title: Crystal structure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crystal_structure
date_saved: 2026-05-05T10:52:12.114890+00:00
instance: kb-cron
parent: crystal-structure-20260505-0
summary:
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in a material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice. The lengths of principal axes/edges, of the unit cell and angles between them are lattice constants, also called lattice parameters or cell parameters. The symmetry properties of a crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space may be described by 230 space groups. The crystal structure and symmetry play a critical role in determining many physical properties, such as cleavage, electronic band structure, and optical transparency. == Unit cell == Crystal structure is described in terms of the geometry of the arrangement of particles in the unit


id: crystal-structure-20260505-1
file: data/en.wikipedia.org/wiki/Crystal_structure-1.md
category: reference
title: Crystal structure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crystal_structure
date_saved: 2026-05-05T10:52:12.114890+00:00
instance: kb-cron
parent: crystal-structure-20260505-0
summary:
Coordinates in angle brackets such as ⟨100⟩ denote a family of directions that are equivalent due to symmetry operations, such as [100], [010], [001] or the negative of any of those directions. Coordinates in curly brackets or braces such as {100} denote a family of plane normals that are equivalent due to symmetry operations, much the way angle brackets denote a family of directions. For face-centered cubic (fcc) and body-centered cubic (bcc) lattices, the primitive lattice vectors are not orthogonal. However, in these cases the Miller indices are conventionally defined relative to the lattice vectors of the cubic supercell and hence are again simply the Cartesian directions. === Interplanar spacing === The perpendicular spacing d between adjacent (hkℓ) lattice planes is given by: Cubic: 1 d 2 = h 2 + k 2 + ℓ 2 a 2 {\displaystyle {\frac {1}{d^{2}}}={\frac {h^{2}+k^{2}+\ell ^{2}}{a^{2}}}} Tetragonal: 1 d 2 = h 2 + k 2 a 2 + ℓ 2 c 2 {\displaystyle {\frac {1}{d^{2}}}={\frac {h^{2}+k^{2}}{a^{2}}}+{\frac {\ell ^{2}}{c^{2}}}} Hexagonal: 1 d 2 = 4 3 ( h 2 + h k + k 2 a 2 ) + ℓ 2 c 2 {\displaystyle {\frac {1}{d^{2}}}={\frac {4}{3}}\left({\frac {h^{2}+hk+k^{2}}{a^{2}}}\right)+{\frac {\ell ^{2}}{c^{2}}}} Rhombohedral (primitive setting):


id: crystal-structure-20260505-2
file: data/en.wikipedia.org/wiki/Crystal_structure-2.md
category: reference
title: Crystal structure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crystal_structure
date_saved: 2026-05-05T10:52:12.114890+00:00
instance: kb-cron
parent: crystal-structure-20260505-0
summary:
A crystal system is a set of point groups in which the point groups themselves and their corresponding space groups are assigned to a lattice system. Of the 32 point groups that exist in three dimensions, most are assigned to only one lattice system, in which case the crystal system and lattice system both have the same name. However, five point groups are assigned to two lattice systems, rhombohedral and hexagonal, because both lattice systems exhibit threefold rotational symmetry. These point groups are assigned to the trigonal crystal system. In total there are seven crystal systems: triclinic, monoclinic, orthorhombic, tetragonal, trigonal, hexagonal, and cubic. ==== Point groups ==== The crystallographic point group or crystal class is the mathematical group comprising the symmetry operations that leave at least one point unmoved and that leave the appearance of the crystal structure unchanged. These symmetry operations include Reflection, which reflects the structure across a reflection plane Rotation, which rotates the structure a specified portion of a circle about a rotation axis Inversion, which changes the sign of the coordinate of each point with respect to a center of symmetry or inversion point Improper rotation, which consists of a rotation about an axis followed


id: crystal-structure-20260505-3
file: data/en.wikipedia.org/wiki/Crystal_structure-3.md
category: reference
title: Crystal structure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crystal_structure
date_saved: 2026-05-05T10:52:12.114890+00:00
instance: kb-cron
parent: crystal-structure-20260505-0
summary:
Grain boundaries are interfaces where crystals of different orientations meet. A grain boundary is a single-phase interface, with crystals on each side of the boundary being identical except in orientation. The term "crystallite boundary" is sometimes, though rarely, used. Grain boundary areas contain those atoms that have been perturbed from their original lattice sites, dislocations, and impurities that have migrated to the lower energy grain boundary. Treating a grain boundary geometrically as an interface of a single crystal cut into two parts, one of which is rotated, we see that there are five variables required to define a grain boundary. The first two numbers come from the unit vector that specifies a rotation axis. The third number designates the angle of rotation of the grain. The final two numbers specify the plane of the grain boundary (or a unit vector that is normal to this plane). Grain boundaries disrupt the motion of dislocations through a material, so reducing crystallite size is a common way to improve strength, as described by the Hall–Petch relationship. Since grain boundaries are defects in the crystal structure they tend to decrease the electrical and thermal conductivity of the material. The high interfacial energy and relatively


id: crystal-structure-20260505-4
file: data/en.wikipedia.org/wiki/Crystal_structure-4.md
category: reference
title: Crystal structure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crystal_structure
date_saved: 2026-05-05T10:52:12.114890+00:00
instance: kb-cron
parent: crystal-structure-20260505-0
summary:
Polymorphism is the occurrence of multiple crystalline forms of a material. It is found in many crystalline materials including polymers, minerals, and metals. According to Gibbs' rules of phase equilibria, these unique crystalline phases are dependent on intensive variables such as pressure and temperature. Polymorphism is related to allotropy, which refers to elemental solids. The complete morphology of a material is described by polymorphism and other variables such as crystal habit, amorphous fraction or crystallographic defects. Polymorphs have different stabilities and may spontaneously and irreversibly transform from a metastable form (or thermodynamically unstable form) to the stable form at a particular temperature. They also exhibit different melting points, solubilities, and X-ray diffraction patterns. One good example of this is the quartz form of silicon dioxide, or SiO2. In the vast majority of silicates, the Si atom shows tetrahedral coordination by 4 oxygens. All but one of the crystalline forms involve tetrahedral {SiO4} units linked together by shared vertices in different arrangements. In different minerals the tetrahedra show different degrees of networking and polymerization. For example, they occur singly, joined in pairs, in larger finite clusters including rings, in chains, double chains, sheets, and three-dimensional frameworks. The minerals are classified into


id: defining-equation-physical-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Defining_equation_(physical_chemistry)-0.md
category: reference
title: Defining equation (physical chemistry)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Defining_equation_(physical_chemistry)
date_saved: 2026-05-05T10:52:13.451525+00:00
instance: kb-cron
parent: defining-equation-physical-chemistry-20260505-0
summary:
In physical chemistry, there are numerous quantities associated with chemical compounds and reactions; notably in terms of amounts of substance, activity or concentration of a substance, and the rate of reaction. This article uses SI units. == Introduction == Theoretical chemistry requires quantities from core physics, such as time, volume, temperature, and pressure. But the highly quantitative nature of physical chemistry, in a more specialized way than core physics, uses molar amounts of substance rather than simply counting numbers; this leads to the specialized definitions in this article. Core physics itself rarely uses the mole, except in areas overlapping thermodynamics and chemistry. == Notes on nomenclature == Entity refers to the type of particle/s in question, such as atoms, molecules, complexes, radicals, ions, electrons etc. Conventionally for concentrations and activities, square brackets [ ] are used around the chemical molecular formula. For an arbitrary atom, generic letters in upright non-bold typeface such as A, B, R, X or Y etc. are often used. No standard symbols are used for the following quantities, as specifically applied to a substance: the mass of a substance m, the number of moles of the substance n, partial pressure of a gas in a gaseous


id: dopant-20260505-0
file: data/en.wikipedia.org/wiki/Dopant-0.md
category: reference
title: Dopant
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dopant
date_saved: 2026-05-05T10:52:14.596201+00:00
instance: kb-cron
parent: dopant-20260505-0
summary:
A dopant (also called a doping agent) is a small amount of a substance added to a material to alter its physical properties, such as electrical or optical properties. The amount of dopant is typically very low compared to the material being doped. When doped into crystalline substances, the dopant's atoms get incorporated into the crystal lattice of the substance. The crystalline materials are frequently either crystals of a semiconductor such as silicon and germanium for use in solid-state electronics, or transparent crystals for use in the production of various laser types; however, in some cases of the latter, noncrystalline substances such as glass can also be doped with impurities. In solid-state electronics using the proper types and amounts of dopants in semiconductors is what produces the p-type semiconductors and n-type semiconductors that are essential for making transistors and diodes. == Transparent crystals == === Lasing media === The procedure of doping tiny amounts of the metals chromium (Cr), neodymium (Nd), erbium (Er), thulium (Tm), ytterbium (Yb), and a few others, into transparent crystals, ceramics, or glasses is used to produce the active medium for solid-state lasers. It is in the electrons of the dopant atoms that a population inversion


id: elastic-properties-of-the-elements-data-page-20260505-0
file: data/en.wikipedia.org/wiki/Elastic_properties_of_the_elements_(data_page)-0.md
category: reference
title: Elastic properties of the elements (data page)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Elastic_properties_of_the_elements_(data_page)
date_saved: 2026-05-05T10:52:15.843961+00:00
instance: kb-cron
parent: elastic-properties-of-the-elements-data-page-20260505-0
summary:
Elastic properties describe the reversible deformation (elastic response) of a material to an applied stress. They are a subset of the material properties that provide a quantitative description of the characteristics of a material, like its strength. Material properties are most often characterized by a set of numerical parameters called moduli. The elastic properties can be well-characterized by the Young's modulus, Poisson's ratio, Bulk modulus, and Shear modulus or they may be described by the Lamé parameters. == Young's modulus == == Poisson's ratio == == Bulk modulus == == Shear modulus == == References == == See also ==


id: electric-charge-20260505-0
file: data/en.wikipedia.org/wiki/Electric_charge-0.md
category: reference
title: Electric charge
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electric_charge
date_saved: 2026-05-05T10:52:17.037385+00:00
instance: kb-cron
parent: electric-charge-20260505-0
summary:
Electric charge (symbol q, sometimes Q) is a physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be positive or negative. Like charges repel each other and unlike charges attract each other. An object with no net charge is referred to as electrically neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum effects. In an isolated system, the total charge stays the same - the amount of positive charge minus the amount of negative charge does not change over time. Electric charge carriers include subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms. If there are more electrons than protons in a piece of matter, it will have a negative charge, if there are fewer it will have a positive charge, and if there are equal numbers it will be neutral. Charge is quantized: it comes in integer multiples of individual small units called the elementary charge, e, about 1.602×10−19 C, which is the smallest charge that


id: electric-charge-20260505-1
file: data/en.wikipedia.org/wiki/Electric_charge-1.md
category: reference
title: Electric charge
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electric_charge
date_saved: 2026-05-05T10:52:17.037385+00:00
instance: kb-cron
parent: electric-charge-20260505-0
summary:
During the formation of macroscopic objects, constituent atoms and ions usually combine to form structures composed of neutral ionic compounds electrically bound to neutral atoms. Thus macroscopic objects tend toward being neutral overall, but macroscopic objects are rarely perfectly net neutral. Sometimes macroscopic objects contain ions distributed throughout the material, rigidly bound in place, giving an overall net positive or negative charge to the object. Also, macroscopic objects made of conductive elements can more or less easily (depending on the element) take on or give off electrons, and then maintain a net negative or positive charge indefinitely. When the net electric charge of an object is non-zero and motionless, the phenomenon is known as static electricity. This can easily be produced by rubbing two dissimilar materials together, such as rubbing amber with fur or glass with silk. In this way, non-conductive materials can be charged to a significant degree, either positively or negatively. Charge taken from one material is moved to the other material, leaving an opposite charge of the same magnitude behind. The law of conservation of charge always applies, giving the object from which a negative charge is taken a positive charge of the same magnitude, and vice


id: electric-charge-20260505-2
file: data/en.wikipedia.org/wiki/Electric_charge-2.md
category: reference
title: Electric charge
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electric_charge
date_saved: 2026-05-05T10:52:17.037385+00:00
instance: kb-cron
parent: electric-charge-20260505-0
summary:
From ancient times, people were familiar with four types of phenomena that today would all be explained using the concept of electric charge: (a) lightning, (b) the torpedo fish (or electric ray), (c) St Elmo's Fire, and (d) that amber rubbed with fur would attract small, light objects. The first account of the amber effect is often attributed to the ancient Greek mathematician Thales of Miletus, who lived from c. 624 to c. 546 BC, but there are doubts about whether Thales left any writings; his account about amber is known from an account from early 200s. This account can be taken as evidence that the phenomenon was known since at least c. 600 BC, but Thales explained this phenomenon as evidence for inanimate objects having a soul. In other words, there was no indication of any conception of electric charge. More generally, the ancient Greeks did not understand the connections among these four kinds of phenomena. The Greeks observed that the charged amber buttons could attract light objects such as hair. They also found that if they rubbed the amber for long enough, they could even get an electric spark to jump, but there is also a claim that


id: electric-charge-20260505-3
file: data/en.wikipedia.org/wiki/Electric_charge-3.md
category: reference
title: Electric charge
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electric_charge
date_saved: 2026-05-05T10:52:17.037385+00:00
instance: kb-cron
parent: electric-charge-20260505-0
summary:
Franklin had studied some of Watson's works prior to making his own experiments and analysis, which was probably significant for Franklin's own theorizing. One physicist suggests that Watson first proposed a one-fluid theory, which Franklin then elaborated further and more influentially. A historian of science argues that Watson missed a subtle difference between his ideas and Franklin's, so that Watson misinterpreted his ideas as being similar to Franklin's. In any case, there was no animosity between Watson and Franklin, and the Franklin model of electrical action, formulated in early 1747, eventually became widely accepted at that time. After Franklin's work, effluvia-based explanations were rarely put forward. It is now known that the Franklin model was fundamentally correct. There is only one kind of electrical charge, and only one variable is required to keep track of the amount of charge. Until 1800 it was only possible to study conduction of electric charge by using an electrostatic discharge. In 1800 Alessandro Volta was the first to show that charge could be maintained in continuous motion through a closed path. In 1833, Michael Faraday sought to remove any doubt that electricity is identical, regardless of the source by which it is produced. He


id: electric-charge-20260505-4
file: data/en.wikipedia.org/wiki/Electric_charge-4.md
category: reference
title: Electric charge
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electric_charge
date_saved: 2026-05-05T10:52:17.037385+00:00
instance: kb-cron
parent: electric-charge-20260505-0
summary:
== Role of charge in static electricity == Static electricity refers to the electric charge of an object and the related electrostatic discharge when two objects are brought together that are not at equilibrium. An electrostatic discharge creates a change in the charge of each of the two objects. === Electrification by sliding === When a piece of glass and a piece of resin—neither of which exhibit any electrical properties—are rubbed together and left with the rubbed surfaces in contact, they still exhibit no electrical properties. When separated, they attract each other. A second piece of glass rubbed with a second piece of resin, then separated and suspended near the former pieces of glass and resin causes these phenomena: The two pieces of glass repel each other. Each piece of glass attracts each piece of resin. The two pieces of resin repel each other. This attraction and repulsion is an electrical phenomenon, and the bodies that exhibit them are said to be electrified, or electrically charged. Bodies may be electrified in many other ways, as well as by sliding. The electrical properties of the two pieces of glass are similar to each other but opposite to those of the two


id: electrical-resistivities-of-the-elements-data-page-20260505-0
file: data/en.wikipedia.org/wiki/Electrical_resistivities_of_the_elements_(data_page)-0.md
category: reference
title: Electrical resistivities of the elements (data page)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrical_resistivities_of_the_elements_(data_page)
date_saved: 2026-05-05T10:52:18.259638+00:00
instance: kb-cron
parent: electrical-resistivities-of-the-elements-data-page-20260505-0
summary:
== Electrical resistivity == == References == === WEL === As quoted at http://www.webelements.com/ from these sources: G.W.C. Kaye and T. H. Laby in Tables of physical and chemical constants, Longman, London, UK, 15th edition, 1993. A.M. James and M.P. Lord in Macmillan's Chemical and Physical Data, Macmillan, London, UK, 1992. D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 79th edition, 1998. J.A. Dean (ed) in Lange's Handbook of Chemistry, McGraw-Hill, New York, USA, 14th edition, 1992. === CRC === As quoted from various sources in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press. Boca Raton, Florida, 2003; Section 12, Properties of Solids; Electrical Resistivity of Pure Metals === CR2 === As quoted in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press. Boca Raton, Florida, 2003; Section 4, Properties of the Elements and Inorganic Compounds; Physical Properties of the Rare Earth Metals which further refers to: Beaudry, B. J. and Gschneidner, K.A., Jr., in Handbook on the Physics and Chemistry of Rare Earths, Vol. 1, Gschneidner, K.A., Jr. and Eyring,


id: electron-affinity-20260505-0
file: data/en.wikipedia.org/wiki/Electron_affinity-0.md
category: reference
title: Electron affinity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_affinity
date_saved: 2026-05-05T10:52:19.434128+00:00
instance: kb-cron
parent: electron-affinity-20260505-0
summary:
The electron affinity (Eea) of an atom or molecule is defined as the amount of energy released when an electron attaches to a neutral atom or molecule in the gaseous state to form an anion. X(g) + e− → X−(g) + energy This differs by sign from the energy change of electron capture ionization. The electron affinity is positive when energy is released on electron capture. In solid state physics, the electron affinity for a surface is defined somewhat differently. == Measurement and use of electron affinity == This property is used to measure atoms and molecules in the gaseous state only, since in a solid or liquid state their energy levels would be changed by contact with other atoms or molecules. A list of the electron affinities was used by Robert S. Mulliken to develop an electronegativity scale for atoms, equal to the average of the electrons affinity and ionization potential. Other theoretical concepts that use electron affinity include electronic chemical potential and chemical hardness. Another example, a molecule or atom that has a more positive value of electron affinity than another is often called an electron acceptor and the less positive an electron donor. Together they may undergo


id: electron-affinity-20260505-1
file: data/en.wikipedia.org/wiki/Electron_affinity-1.md
category: reference
title: Electron affinity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_affinity
date_saved: 2026-05-05T10:52:19.434128+00:00
instance: kb-cron
parent: electron-affinity-20260505-0
summary:
In an intrinsic semiconductor at absolute zero, this concept is functionally analogous to the chemistry definition of electron affinity, since an added electron will spontaneously go to the bottom of the conduction band. At nonzero temperature, and for other materials (metals, semimetals, heavily doped semiconductors), the analogy does not hold since an added electron will instead go to the Fermi level on average. In any case, the value of the electron affinity of a solid substance is very different from the chemistry and atomic physics electron affinity value for an atom of the same substance in gas phase. For example, a silicon crystal surface has electron affinity 4.05 eV, whereas an isolated silicon atom has electron affinity 1.39 eV. The electron affinity of a surface is closely related to its work function. The work function is the thermodynamic work that can be obtained by reversibly and isothermally removing an electron from the material to vacuum; this thermodynamic electron goes to the Fermi level on average, not the conduction band edge: W = E v a c − E F {\displaystyle W=E_{\rm {vac}}-E_{\rm {F}}} . While the work function of a semiconductor can be changed by doping, the electron affinity ideally


id: electron-affinity-data-page-20260505-0
file: data/en.wikipedia.org/wiki/Electron_affinity_(data_page)-0.md
category: reference
title: Electron affinity (data page)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_affinity_(data_page)
date_saved: 2026-05-05T10:52:20.779211+00:00
instance: kb-cron
parent: electron-affinity-data-page-20260505-0
summary:
This page deals with the electron affinity as a property of isolated atoms or molecules (i.e. in the gas phase). Solid state electron affinities are not listed here. == Elements == Electron affinity can be defined in two equivalent ways. First, as the energy that is released by adding an electron to an isolated gaseous atom. The second (reverse) definition is that electron affinity is the energy required to remove an electron from a singly charged gaseous negative ion. The latter can be regarded as the ionization energy of the −1 ion or the zeroth ionization energy. Either convention can be used. Negative electron affinities can be used in those cases where electron capture requires energy, i.e. when capture can occur only if the impinging electron has a kinetic energy large enough to excite a resonance of the atom-plus-electron system. Conversely electron removal from the anion formed in this way releases energy, which is carried out by the freed electron as kinetic energy. Negative ions formed in these cases are always unstable. They may have lifetimes of the order of microseconds to milliseconds, and invariably autodetach after some time. † A quantum offset of the velocity imaging-based measurements was revealed


id: electron-configuration-20260505-0
file: data/en.wikipedia.org/wiki/Electron_configuration-0.md
category: reference
title: Electron configuration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_configuration
date_saved: 2026-05-05T10:52:21.981173+00:00
instance: kb-cron
parent: electron-configuration-20260505-0
summary:
In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom is 1s2 2s2 2p6, meaning that the 1s, 2s, and 2p subshells are occupied by two, two, and six electrons, respectively. Electronic configurations describe each electron as moving independently in an orbital, in an average field created by the nuclei and all the other electrons. Mathematically, configurations are described by Slater determinants or configuration state functions. According to the laws of quantum mechanics, a level of energy is associated with each electron configuration. In certain conditions, electrons are able to move from one configuration to another by the emission or absorption of a quantum of energy, in the form of a photon. Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elements, for describing the chemical bonds that hold atoms together, and in understanding the chemical formulas of compounds and the geometries of molecules. In bulk materials, this same idea helps explain the peculiar properties of lasers and semiconductors. == Shells and subshells


id: electron-configuration-20260505-1
file: data/en.wikipedia.org/wiki/Electron_configuration-1.md
category: reference
title: Electron configuration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_configuration
date_saved: 2026-05-05T10:52:21.981173+00:00
instance: kb-cron
parent: electron-configuration-20260505-0
summary:
=== Order === For a given configuration, the order of writing the orbitals is not completely fixed since only the orbital occupancies have physical significance. For example, the electron configuration of the titanium ground state can be written as either [Ar] 4s2 3d2 or [Ar] 3d2 4s2. The first notation follows the order based on the Madelung rule for the configurations of neutral atoms; 4s is filled before 3d in the sequence Ar, K, Ca, Sc, Ti. The second notation groups all orbitals with the same value of n together, corresponding to the "spectroscopic" order of orbital energies that is the reverse of the order in which electrons are removed from a given atom to form positive ions; 3d is filled before 4s in the sequence Ti4+, Ti3+, Ti2+, Ti+, Ti. === Implied Values === The superscript 1 for a singly occupied subshell is not compulsory; for example, aluminium may be written as either [Ne] 3s2 3p1 or [Ne] 3s2 3p. In atoms where a subshell is unoccupied despite higher subshells being occupied (as is the case in some ions, as well as certain neutral atoms shown to deviate from the Madelung rule), the empty subshell is either denoted with


id: electron-configuration-20260505-2
file: data/en.wikipedia.org/wiki/Electron_configuration-2.md
category: reference
title: Electron configuration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_configuration
date_saved: 2026-05-05T10:52:21.981173+00:00
instance: kb-cron
parent: electron-configuration-20260505-0
summary:
The Schrödinger equation, published in 1926, gave three of the four quantum numbers as a direct consequence of its solution for the hydrogen atom: this solution yields the atomic orbitals that are shown today in textbooks of chemistry (and above). The examination of atomic spectra allowed the electron configurations of atoms to be determined experimentally, and led to an empirical rule (known as Madelung's rule (1936), see below) for the order in which atomic orbitals are filled with electrons. == Atoms: Aufbau principle and Madelung rule == The aufbau principle (from the German Aufbau, "building up, construction") was an important part of Bohr's original concept of electron configuration. It may be stated as: a maximum of two electrons are put into orbitals in the order of increasing orbital energy: the lowest-energy subshells are filled before electrons are placed in higher-energy orbitals. The principle works very well (for the ground states of the atoms) for the known 118 elements, although it is sometimes slightly wrong. The modern form of the aufbau principle describes an order of orbital energies given by Madelung's rule (or Klechkowski's rule). This rule was first stated by Charles Janet in 1929, rediscovered by Erwin Madelung in 1936,


id: electron-configuration-20260505-3
file: data/en.wikipedia.org/wiki/Electron_configuration-3.md
category: reference
title: Electron configuration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_configuration
date_saved: 2026-05-05T10:52:21.981173+00:00
instance: kb-cron
parent: electron-configuration-20260505-0
summary:
=== Ionization of the transition metals === The naïve application of the aufbau principle leads to a well-known paradox (or apparent paradox) in the basic chemistry of the transition metals. Potassium and calcium appear in the periodic table before the transition metals, and have electron configurations [Ar] 4s1 and [Ar] 4s2 respectively, i.e. the 4s-orbital is filled before the 3d-orbital. This is in line with Madelung's rule, as the 4s-orbital has n + l = 4 (n = 4, l = 0) while the 3d-orbital has n + l = 5 (n = 3, l = 2). After calcium, most neutral atoms in the first series of transition metals (scandium through zinc) have configurations with two 4s electrons, but there are two exceptions. Chromium and copper have electron configurations [Ar] 3d5 4s1 and [Ar] 3d10 4s1 respectively, i.e. one electron has passed from the 4s-orbital to a 3d-orbital to generate a half-filled or filled subshell. In this case, the usual explanation is that "half-filled or completely filled subshells are particularly stable arrangements of electrons". However, this is not supported by the facts, as tungsten (W) has a Madelung-following d4 s2 configuration and not d5 s1, and niobium (Nb) has an


id: electron-configuration-20260505-4
file: data/en.wikipedia.org/wiki/Electron_configuration-4.md
category: reference
title: Electron configuration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_configuration
date_saved: 2026-05-05T10:52:21.981173+00:00
instance: kb-cron
parent: electron-configuration-20260505-0
summary:
=== Other exceptions to Madelung's rule === There are several more exceptions to Madelung's rule among the heavier elements, and as atomic number increases it becomes more and more difficult to find simple explanations such as the stability of half-filled subshells. It is possible to predict most of the exceptions by Hartree–Fock calculations, which are an approximate method for taking account of the effect of the other electrons on orbital energies. Qualitatively, for example, the 4d elements have the greatest concentration of Madelung anomalies, because the 4d–5s gap is larger than the 3d–4s and 5d–6s gaps. For the heavier elements, it is also necessary to take account of the effects of special relativity on the energies of the atomic orbitals, as the inner-shell electrons are moving at speeds approaching the speed of light. In general, these relativistic effects tend to decrease the energy of the s-orbitals in relation to the other atomic orbitals. This is the reason why the 6d elements are predicted to have no Madelung anomalies apart from lawrencium (for which relativistic effects stabilise the p1/2 orbital as well and cause its occupancy in the ground state), as relativity intervenes to make the 7s orbitals lower in energy


id: electron-configuration-20260505-5
file: data/en.wikipedia.org/wiki/Electron_configuration-5.md
category: reference
title: Electron configuration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_configuration
date_saved: 2026-05-05T10:52:21.981173+00:00
instance: kb-cron
parent: electron-configuration-20260505-0
summary:
Every system has the tendency to acquire the state of stability or a state of minimum energy, and so chemical elements take part in chemical reactions to acquire a stable electronic configuration similar to that of its nearest noble gas. An example of this tendency is two hydrogen (H) atoms reacting with one oxygen (O) atom to form water (H2O). Neutral atomic hydrogen has one electron in its valence shell, and on formation of water it acquires a share of a second electron coming from oxygen, so that its configuration is similar to that of its nearest noble gas helium (He) with two electrons in its valence shell. Similarly, neutral atomic oxygen has six electrons in its valence shell, and acquires a share of two electrons from the two hydrogen atoms, so that its configuration is similar to that of its nearest noble gas neon with eight electrons in its valence shell. == Electron configuration in molecules == Electron configuration in molecules is more complex than the electron configuration of atoms, as each molecule has a different orbital structure. The molecular orbitals are labelled according to their symmetry, rather than the atomic orbital labels used for atoms and monatomic ions;


id: electronegativities-of-the-elements-data-page-20260505-0
file: data/en.wikipedia.org/wiki/Electronegativities_of_the_elements_(data_page)-0.md
category: reference
title: Electronegativities of the elements (data page)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electronegativities_of_the_elements_(data_page)
date_saved: 2026-05-05T10:52:23.163200+00:00
instance: kb-cron
parent: electronegativities-of-the-elements-data-page-20260505-0
summary:
== Electronegativity (Pauling scale) == == Notes == Separate values for each source are only given where one or more sources differ. Electronegativity is not a uniquely defined property and may depend on the definition. The suggested values are all taken from WebElements as a consistent set. Many of the highly radioactive elements have values that must be predictions or extrapolations, but are unfortunately not marked as such. This is especially problematic for francium, which by relativistic calculations can be shown to be less electronegative than caesium, but for which the only value (0.7) in the literature predates these calculations. == Electronegativity (Allen scale) == == References == Section names here refer to the abbreviation in the table. === WEL === As quoted at http://www.webelements.com/ from these sources: A.L. Allred, J. Inorg. Nucl. Chem., 1961, 17, 215. J.E. Huheey, E.A. Keiter, and R.L. Keiter in Inorganic Chemistry : Principles of Structure and Reactivity, 4th edition, HarperCollins, New York, USA, 1993. === CRC === As quoted from these sources in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press. Boca Raton, Florida, 2003; Section 9, Molecular Structure and Spectroscopy; Electronegativity Pauling, L.,


id: electronegativity-20260505-0
file: data/en.wikipedia.org/wiki/Electronegativity-0.md
category: reference
title: Electronegativity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electronegativity
date_saved: 2026-05-05T10:52:24.353764+00:00
instance: kb-cron
parent: electronegativity-20260505-0
summary:
Electronegativity, symbolized as χ, is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity, the more an atom or a substituent group attracts electrons. Electronegativity serves as a simple way to quantitatively estimate the bond energy, and the sign and magnitude of a bond's chemical polarity, which characterizes a bond along the continuous scale from covalent to ionic bonding. The loosely defined term electropositivity is the opposite of electronegativity: it characterizes an element's tendency to donate valence electrons. On the most basic level, electronegativity is determined by factors like the nuclear charge (the more protons an atom has, the more "pull" it will have on electrons) and the number and location of other electrons in the atomic shells (the more electrons an atom has, the farther from the nucleus the valence electrons will be, and as a result, the less positive charge they will experience—both because of their increased distance from the nucleus and because the other electrons in


id: electronegativity-20260505-1
file: data/en.wikipedia.org/wiki/Electronegativity-1.md
category: reference
title: Electronegativity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electronegativity
date_saved: 2026-05-05T10:52:24.353764+00:00
instance: kb-cron
parent: electronegativity-20260505-0
summary:
E d ( A B ) = E d ( A A ) + E d ( B B ) 2 + ( χ A − χ B ) 2 e V {\displaystyle E_{\rm {d}}({\rm {AB}})={\frac {E_{\rm {d}}({\rm {AA}})+E_{\rm {d}}({\rm {BB}})}{2}}+(\chi _{\rm {A}}-\chi _{\rm {B}})^{2}{\rm {eV}}} or sometimes, a more accurate fit E d ( A B ) = E d ( A A ) E d ( B B ) + 1.3 ( χ A − χ B ) 2 e V {\displaystyle E_{\rm {d}}({\rm {AB}})={\sqrt {E_{\rm {d}}({\rm {AA}})E_{\rm {d}}({\rm {BB}})}}+1.3(\chi _{\rm {A}}-\chi _{\rm {B}})^{2}{\rm {eV}}} These are approximate equations but they hold with good accuracy. Pauling obtained the first equation by noting that a bond can be approximately represented as a quantum mechanical superposition of a covalent bond and two ionic bond states. The covalent energy of a bond is approximately, by quantum mechanical calculations, the geometric mean of the two energies of covalent bonds of the same molecules, and there is additional energy that comes from ionic factors, i.e. polar character of the bond. The geometric mean is approximately equal to the arithmetic mean—which is applied in the first formula above—when the energies are of a similar


id: electronegativity-20260505-2
file: data/en.wikipedia.org/wiki/Electronegativity-2.md
category: reference
title: Electronegativity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electronegativity
date_saved: 2026-05-05T10:52:24.353764+00:00
instance: kb-cron
parent: electronegativity-20260505-0
summary:
χ = n s ε s + n p ε p n s + n p {\displaystyle \chi ={n_{\rm {s}}\varepsilon _{\rm {s}}+n_{\rm {p}}\varepsilon _{\rm {p}} \over n_{\rm {s}}+n_{\rm {p}}}} where εs,p are the one-electron energies of s- and p-electrons in the free atom and ns,p are the number of s- and p-electrons in the valence shell. The one-electron energies can be determined directly from spectroscopic data, and so electronegativities calculated by this method are sometimes referred to as spectroscopic electronegativities. The necessary data are available for almost all elements, and this method allows the estimation of electronegativities for elements that cannot be treated by the other methods, e.g. francium, which has an Allen electronegativity of 0.67. However, it is not clear what should be considered to be valence electrons for the d- and f-block elements, which leads to an ambiguity regarding their electronegativities calculated by the Allen method. On this scale, neon has the highest electronegativity of all elements, followed by fluorine, helium, and oxygen. == Correlation of electronegativity with other properties == The wide variety of methods of calculation of electronegativities, which all give results that correlate well with one another, is one indication of the number of chemical


id: electronegativity-20260505-3
file: data/en.wikipedia.org/wiki/Electronegativity-3.md
category: reference
title: Electronegativity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electronegativity
date_saved: 2026-05-05T10:52:24.353764+00:00
instance: kb-cron
parent: electronegativity-20260505-0
summary:
== Group electronegativity == In organic chemistry, electronegativity is associated more with different functional groups than with individual atoms. The terms group electronegativity and substituent electronegativity are used synonymously. However, it is common to distinguish between the inductive effect and the resonance effect, which might be described as σ- and π-electronegativities, respectively. There are several linear free-energy relationships that have been used to quantify these effects, of which the Hammett equation is the best known. Kabachnik Parameters are group electronegativities for use in organophosphorus chemistry. == Electropositivity == Electropositivity is a measure of an element's ability to donate electrons, and therefore form positive ions; thus, it is antipode to electronegativity. Mainly, this is an attribute of metals, meaning that, in general, the greater the metallic character of an element the greater the electropositivity. Therefore, the alkali metals are the most electropositive of all. This is because they have a single electron in their outer shell and, as this is relatively far from the nucleus of the atom, it is easily lost; in other words, these metals have low ionization energies. While electronegativity increases along periods in the periodic table and decreases down groups, electropositivity decreases along periods (from left to


id: energy-level-20260505-0
file: data/en.wikipedia.org/wiki/Energy_level-0.md
category: reference
title: Energy level
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Energy_level
date_saved: 2026-05-05T10:52:25.529347+00:00
instance: kb-cron
parent: energy-level-20260505-0
summary:
A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical particles, which can have any amount of energy. The term is commonly used for the energy levels of the electrons in atoms, ions, or molecules, which are bound by the electric field of the nucleus, but can also refer to energy levels of nuclei or vibrational or rotational energy levels in molecules. The energy spectrum of a system with such discrete energy levels is said to be quantized. In chemistry and atomic physics, an electron shell, or principal energy level, may be thought of as the orbit of one or more electrons around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" (also called "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on further and further from the nucleus. The shells correspond with the principal quantum numbers (n = 1, 2, 3, 4, ...) or are labeled alphabetically with letters used in the X-ray notation (K, L, M, N, ...). Each shell can contain only a fixed


id: energy-level-20260505-1
file: data/en.wikipedia.org/wiki/Energy_level-1.md
category: reference
title: Energy level
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Energy_level
date_saved: 2026-05-05T10:52:25.529347+00:00
instance: kb-cron
parent: energy-level-20260505-0
summary:
1 λ = R Z 2 ( 1 n 1 2 − 1 n 2 2 ) {\displaystyle {\frac {1}{\lambda }}=RZ^{2}\left({\frac {1}{n_{1}^{2}}}-{\frac {1}{n_{2}^{2}}}\right)} An equivalent formula can be derived quantum mechanically from the time-independent Schrödinger equation with a kinetic energy Hamiltonian operator using a wave function as an eigenfunction to obtain the energy levels as eigenvalues, but the Rydberg constant would be replaced by other fundamental physics constants. ==== Electron–electron interactions in atoms ==== If there is more than one electron around the atom, electron–electron interactions raise the energy level. These interactions are often neglected if the spatial overlap of the electron wavefunctions is low. For multi-electron atoms, interactions between electrons cause the preceding equation to be no longer accurate as stated simply with Z as the atomic number. A simple (though not complete) way to understand this is as a shielding effect, where the outer electrons see an effective nucleus of reduced charge, since the inner electrons are bound tightly to the nucleus and partially cancel its charge. This leads to an approximate correction where Z is substituted with an effective nuclear charge symbolized as Zeff that depends strongly on the principal quantum number. E n , ℓ =


id: energy-level-20260505-2
file: data/en.wikipedia.org/wiki/Energy_level-2.md
category: reference
title: Energy level
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Energy_level
date_saved: 2026-05-05T10:52:25.529347+00:00
instance: kb-cron
parent: energy-level-20260505-0
summary:
Electrons in atoms and molecules can change (make transitions in) energy levels by emitting or absorbing a photon (of electromagnetic radiation), whose energy must be exactly equal to the energy difference between the two levels. Electrons can also be completely removed from a chemical species such as an atom, molecule, or ion. Complete removal of an electron from an atom can be a form of ionization, which is effectively moving the electron out to an orbital with an infinite principal quantum number, in effect so far away so as to have practically no more effect on the remaining atom (ion). For various types of atoms, there are 1st, 2nd, 3rd, etc. ionization energies for removing the 1st, then the 2nd, then the 3rd, etc. of the highest energy electrons, respectively, from the atom originally in the ground state. Energy in corresponding opposite quantities can also be released, sometimes in the form of photon energy, when electrons are added to positively charged ions or sometimes atoms. Molecules can also undergo transitions in their vibrational or rotational energy levels. Energy level transitions can also be nonradiative, meaning emission or absorption of a photon is not involved. If an atom, ion, or molecule


id: ester-value-20260505-0
file: data/en.wikipedia.org/wiki/Ester_value-0.md
category: reference
title: Ester value
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ester_value
date_saved: 2026-05-05T10:52:26.739008+00:00
instance: kb-cron
parent: ester-value-20260505-0
summary:
The ester value (EV) is an analytical parameter used in chemistry to determine the amount of ester present in fats and oils. It represents the number of milligrams of potassium hydroxide (KOH) required to saponify the ester content in 1 gram of a substance, and is equivalent to the difference of the saponification value and the acid value. == See also == Acid value Iodine value Saponification value Triglyceride Fatty acid == References ==


