# kb

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 ==


id: field-effect-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Field_effect_(chemistry)-0.md
category: reference
title: Field effect (chemistry)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Field_effect_(chemistry)
date_saved: 2026-05-05T10:52:27.928593+00:00
instance: kb-cron
parent: field-effect-chemistry-20260505-0
summary:
A field effect is the polarization of a molecule through space. The effect is a result of an electric field produced by charge localization in a molecule. This field, which is substituent and conformation dependent, can influence structure and reactivity by manipulating the location of electron density in bonds and/or the overall molecule. The polarization of a molecule through its bonds is a separate phenomenon known as induction. Field effects are relatively weak, and diminish rapidly with distance, but have still been found to alter molecular properties such as acidity. == Field sources == Field effects can arise from the electric dipole field of a bond containing an electronegative atom or electron-withdrawing substituent, as well as from an atom or substituent bearing a formal charge. The directionality of a dipole, and concentration of charge, can both define the shape of a molecule's electric field which will manipulate the localization of electron density toward or away from sites of interest, such as an acidic hydrogen. Field effects are typically associated with the alignment of a dipole field with respect to a reaction center. Since these are through space effects, the 3D structure of a molecule is an important consideration. A field


id: fire-point-20260505-0
file: data/en.wikipedia.org/wiki/Fire_point-0.md
category: reference
title: Fire point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fire_point
date_saved: 2026-05-05T10:52:29.104476+00:00
instance: kb-cron
parent: fire-point-20260505-0
summary:
The fire point, or combustion point, of a fuel is the lowest temperature at which the liquid fuel will continue to burn for at least five seconds after ignition by an open flame of standard dimension. At the flash point, a lower temperature, a substance will ignite briefly, but vapour might not be produced at a rate to sustain the fire. Most tables of material properties will only list material flash points. In general, the fire point can be assumed to be about 10 °C higher than the flash point, although this is no substitute for testing if the fire point is safety critical. Testing of the fire point is done by open cup apparatus. == See also == Autoignition temperature Flash point == Notes ==


id: freezing-point-depression-20260505-0
file: data/en.wikipedia.org/wiki/Freezing-point_depression-0.md
category: reference
title: Freezing-point depression
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Freezing-point_depression
date_saved: 2026-05-05T10:52:30.312205+00:00
instance: kb-cron
parent: freezing-point-depression-20260505-0
summary:
Freezing-point depression is a drop in the maximum temperature at which a substance freezes, caused when a smaller amount of another, non-volatile substance is added. Examples include adding salt into water (used in ice cream makers and for de-icing roads), alcohol in water, ethylene or propylene glycol in water (used in antifreeze in cars), adding copper to molten silver (used to make solder that flows at a lower temperature than the silver pieces being joined), or the mixing of two solids such as impurities into a finely powdered drug. In all cases, the substance added/present in smaller amounts is considered the solute, while the original substance present in larger quantity is thought of as the solvent. The resulting liquid solution or solid-solid mixture has a lower freezing point than the pure solvent or solid because the chemical potential of the solvent in the mixture is lower than that of the pure solvent, the difference between the two being proportional to the natural logarithm of the mole fraction. In a similar manner, the chemical potential of the vapor above the solution is lower than that above a pure solvent, which results in boiling-point elevation. Freezing-point depression is what causes sea water


id: freezing-point-depression-20260505-1
file: data/en.wikipedia.org/wiki/Freezing-point_depression-1.md
category: reference
title: Freezing-point depression
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Freezing-point_depression
date_saved: 2026-05-05T10:52:30.312205+00:00
instance: kb-cron
parent: freezing-point-depression-20260505-0
summary:
Freezing-point depression is used by some organisms that live in extreme cold. Such creatures have evolved means through which they can produce a high concentration of various compounds such as sorbitol and glycerol. This elevated concentration of solute decreases the freezing point of the water inside them, preventing the organism from freezing solid even as the water around them freezes, or as the air around them becomes very cold. Examples of organisms that produce antifreeze compounds include some species of arctic-living fish such as the rainbow smelt, which produces glycerol and other molecules to survive in frozen-over estuaries during the winter months. In other animals, such as the spring peeper frog (Pseudacris crucifer), the molality is increased temporarily as a reaction to cold temperatures. In the case of the peeper frog, freezing temperatures trigger a large-scale breakdown of glycogen in the frog's liver and subsequent release of massive amounts of glucose into the blood. With the formula below, freezing-point depression can be used to measure the degree of dissociation or the molar mass of the solute. This kind of measurement is called cryoscopy (Greek cryo = cold, scopos = observe; "observe the cold") and relies on exact measurement of the


id: fusibility-20260505-0
file: data/en.wikipedia.org/wiki/Fusibility-0.md
category: reference
title: Fusibility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fusibility
date_saved: 2026-05-05T10:52:31.511342+00:00
instance: kb-cron
parent: fusibility-20260505-0
summary:
The fusibility of a material refers to the ease at which the material can be fused together, or to the temperature or amount of heat required to melt a material. Materials such as solder require a relatively low melting point so that when heat is applied to a joint, the solder will melt before the materials being soldered together melt, i.e. high fusibility. On the other hand, firebricks used for furnace linings only melt at very high temperatures (and then they retract, or decompose, or become fracture-prone) and so have low fusibility. Refractory materials often have low fusibility. == Scientific methods == To find the fusibility of certain compounds/materials, there are 2 methods: === Heat test === The most common test used to determine fusibility is to join two pieces with a variable heat source, increasing the temperature or power used in steps, and testing bond strength for each step. If there is no step with good bond strength after joining, then fusibility is said to be low. === Ash fusibility test === In the context of coal analysis, ash fusibility values of the residual coal ash of a coal are often specified. The values are determined using an empirical


id: galvanic-series-20260505-0
file: data/en.wikipedia.org/wiki/Galvanic_series-0.md
category: reference
title: Galvanic series
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Galvanic_series
date_saved: 2026-05-05T10:52:32.708250+00:00
instance: kb-cron
parent: galvanic-series-20260505-0
summary:
The galvanic series (or electropotential series) determines the nobility of metals and semi-metals. When two metals are submerged in an electrolyte, while also electrically connected by some external conductor, the less noble (base) will experience galvanic corrosion. The rate of corrosion is determined by the electrolyte, the difference in nobility, and the relative areas of the anode and cathode exposed to the electrolyte. The difference can be measured as a difference in voltage potential: the less noble metal is the one with a lower (that is, more negative) electrode potential than the nobler one, and will function as the anode (electron or anion attractor) within the electrolyte device functioning as described above (a galvanic cell). Galvanic reaction is the principle upon which batteries are based. See the table of standard electrode potentials for more details. == Galvanic series (most noble at top) == The following is the galvanic series for stagnant (that is, low oxygen content) seawater. The order may change in different environments. Graphite Palladium Platinum Gold Silver Titanium Stainless steel 316 (passivated) Stainless steel 304 (passivated) Silicon bronze Stainless steel 316 (active) Monel 400 Phosphor bronze Admiralty brass Cupronickel Molybdenum Red brass Brass plating Yellow brass Naval brass


id: gel-point-20260505-0
file: data/en.wikipedia.org/wiki/Gel_point-0.md
category: reference
title: Gel point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gel_point
date_saved: 2026-05-05T10:52:33.889930+00:00
instance: kb-cron
parent: gel-point-20260505-0
summary:
In polymer chemistry, the gel point is an abrupt change in the viscosity of a solution containing polymerizable components. At the gel point, a solution undergoes gelation, as reflected in a loss in fluidity. After the monomer/polymer solution has passed the gel point, internal stress builds up in the gel phase, which can lead to volume shrinkage. Gelation is characteristic of polymerizations that include crosslinkers that can form 2- or 3-dimensional networks. For example, the condensation of a dicarboxylic acid and a triol will give rise to a gel whereas the same dicarboxylic acid and a diol will not. The gel is often a small percentage of the mixture, even though it greatly influences the properties of the bulk. == Mathematical definition == An infinite polymer network appears at the gel point. Assuming that it is possible to measure the extent of reaction, p {\displaystyle p} , defined as the fraction of monomers that appear in cross-links, the gel point can be determined. The critical extent of reaction p c {\displaystyle p_{c}} for the gel point to be formed is given by: p c = 1 N − 1 ≈ 1 N {\displaystyle p_{c}={\frac {1}{N-1}}\approx {\frac {1}{N}}} For example, a


id: gel-point-petroleum-20260505-0
file: data/en.wikipedia.org/wiki/Gel_point_(petroleum)-0.md
category: reference
title: Gel point (petroleum)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gel_point_(petroleum)
date_saved: 2026-05-05T10:52:35.109317+00:00
instance: kb-cron
parent: gel-point-petroleum-20260505-0
summary:
The gel point of petroleum products is the temperature at which the liquids gel so they no longer flow by gravity or can be pumped through fuel lines. This phenomenon happens when the petroleum product reaches a low enough temperature to precipitate interlinked paraffin wax crystals throughout the fluid. More highly distilled petroleum products have fewer paraffins and will have a lower gel point. On the other hand, the gel point of crude oil is dependent upon the composition of the crude oil as some crude oils contain more or less components that dissolve the paraffins. In some cases the gel point of a crude oil may be correlated from the pour point. The gel points of some common petroleum products are as follows: #1 diesel fuel: −9.2 °C (15.4 °F). #2 diesel fuel: −8.1 °C (17.4 °F). Heating oil: −8.9 °C (16.0 °F). Kerosene: −40.0 °C (−40.0 °F). For the petroleum product to flow again, it needs to be brought above the gel point temperature to the ungel point, which is typically near its pour point. However, without stirring the paraffin waxes may still remain in crystal form so the fuel may have to be warmed further to its


id: hydration-number-20260505-0
file: data/en.wikipedia.org/wiki/Hydration_number-0.md
category: reference
title: Hydration number
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hydration_number
date_saved: 2026-05-05T10:52:36.261222+00:00
instance: kb-cron
parent: hydration-number-20260505-0
summary:
The hydration number of a compound is defined as the number of molecules of water bonded to a central ion, often a metal cation. The hydration number is related to the broader concept of solvation number, the number of solvent molecules bonded to a central atom. The hydration number varies with the atom or ion of interest. In aqueous solution, solutes interact with water molecules to varying degrees. Metal cations form aquo complexes, wherein the oxygen of water bind to the cation. This first coordination sphere is encased in further solvation shells, whereby water bonds to the coordinated water via hydrogen bonding. For charged species, the orientation of water molecules around the solute dependent on its radius and charge, with cations attracting water's electronegative oxygen and anions attracting the hydrogens. Uncharged compounds such as methane can also be solvated by water and also have a hydration number. Although solvation shells can contain inner and outer shell solvent-solute interactions, the hydration number generally focuses on the inner shell solvent molecules that directly interact with the solute. Sodium ions are typically surrounded by 4 to 6 water molecules in their primary hydration shell. This arrangement reflects the ion's charge density and size,


id: hydrophile-20260505-0
file: data/en.wikipedia.org/wiki/Hydrophile-0.md
category: reference
title: Hydrophile
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hydrophile
date_saved: 2026-05-05T10:52:37.483114+00:00
instance: kb-cron
parent: hydrophile-20260505-0
summary:
A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water. In contrast, hydrophobes are not attracted to water and may seem to be repelled by it. Hygroscopics are attracted to water, but are not dissolved by water. == Molecules == A hydrophilic molecule or portion of a molecule is one whose interactions with water and other polar substances are more thermodynamically favorable than their interactions with oil or other hydrophobic solvents. They are typically charge-polarized and capable of hydrogen bonding. This makes these molecules soluble not only in water but also in polar solvents. Hydrophilic molecules (and portions of molecules) can be contrasted with hydrophobic molecules (and portions of molecules). In some cases, both hydrophilic and hydrophobic properties occur in a single molecule. An example of these amphiphilic molecules is the lipids that comprise the cell membrane. Another example is soap, which has a hydrophilic head and a hydrophobic tail, allowing it to dissolve in both water and oil. Hydrophilic and hydrophobic molecules are also known as polar molecules and nonpolar molecules, respectively. Some hydrophilic substances do not dissolve. This type of mixture is called a colloid. An


id: hydrophobe-20260505-0
file: data/en.wikipedia.org/wiki/Hydrophobe-0.md
category: reference
title: Hydrophobe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hydrophobe
date_saved: 2026-05-05T10:52:38.672869+00:00
instance: kb-cron
parent: hydrophobe-20260505-0
summary:
In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds. The term hydrophobic—which comes from the Ancient Greek ὑδρόφοβος (hydróphobos), "having a fear of water", constructed from Ancient Greek ὕδωρ (húdōr) 'water' and Ancient Greek φόβος (phóbos) 'fear'—is often used interchangeably with lipophilic, "fat-loving". However, the two terms are not synonymous. While hydrophobic substances are usually lipophilic, there are exceptions, such as the silicones and fluorocarbons. == Chemistry == For small solutes, the hydrophobic interaction is mostly an entropic effect originating from the disruption of the highly dynamic hydrogen bonds between molecules of liquid water by


id: hydrophobe-20260505-1
file: data/en.wikipedia.org/wiki/Hydrophobe-1.md
category: reference
title: Hydrophobe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hydrophobe
date_saved: 2026-05-05T10:52:38.672869+00:00
instance: kb-cron
parent: hydrophobe-20260505-0
summary:
A recent alternative criterion for the Cassie–Baxter state asserts that the Cassie–Baxter state exists when the following 2 criteria are met:1) Contact line forces overcome body forces of unsupported droplet weight and 2) The microstructures are tall enough to prevent the liquid that bridges microstructures from touching the base of the microstructures. A new criterion for the switch between Wenzel and Cassie-Baxter states has been developed recently based on surface roughness and surface energy. The criterion focuses on the air-trapping capability under liquid droplets on rough surfaces, which could tell whether Wenzel's model or Cassie-Baxter's model should be used for certain combination of surface roughness and energy. Contact angle is a measure of static hydrophobicity, and contact angle hysteresis and slide angle are dynamic measures. Contact angle hysteresis is a phenomenon that characterizes surface heterogeneity. When a pipette injects a liquid onto a solid, the liquid will form some contact angle. As the pipette injects more liquid, the droplet will increase in volume, the contact angle will increase, but its three-phase boundary will remain stationary until it suddenly advances outward. The contact angle the droplet had immediately before advancing outward is termed the advancing contact angle. The receding contact angle


id: hydrophobe-20260505-2
file: data/en.wikipedia.org/wiki/Hydrophobe-2.md
category: reference
title: Hydrophobe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hydrophobe
date_saved: 2026-05-05T10:52:38.672869+00:00
instance: kb-cron
parent: hydrophobe-20260505-0
summary:
== Applications and potential applications == Hydrophobic concrete has been produced since the mid-20th century. Active recent research on superhydrophobic materials might eventually lead to more industrial applications. A simple routine of coating cotton fabric with silica or titania particles by sol-gel technique has been reported, which protects the fabric from UV light and makes it superhydrophobic. An efficient routine has been reported for making polyethylene superhydrophobic and thus self-cleaning. 99% of dirt on such a surface is easily washed away. Patterned superhydrophobic surfaces also have promise for lab-on-a-chip microfluidic devices and can drastically improve surface-based bioanalysis. In pharmaceuticals, hydrophobicity of pharmaceutical blends affects important quality attributes of final products, such as drug dissolution and hardness. Methods have been developed to measure the hydrophobicity of pharmaceutical materials. The development of hydrophobic passive daytime radiative cooling (PDRC) surfaces, whose effectiveness at solar reflectance and thermal emittance is predicated on their cleanliness, has improved the "self-cleaning" of these surfaces. Scalable and sustainable hydrophobic PDRCs that avoid VOCs have further been developed. == See also == Froth flotation – Process for selectively separating of hydrophobic materials from hydrophilic Hydrophile – Molecular entity that is attracted to water Hydrophobic effect – Aggregation of non-polar


id: silicon-organic-water-repellent-20260505-0
file: data/en.wikipedia.org/wiki/Silicon_organic_water_repellent-0.md
category: reference
title: Silicon organic water repellent
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Silicon_organic_water_repellent
date_saved: 2026-05-05T10:52:39.863184+00:00
instance: kb-cron
parent: silicon-organic-water-repellent-20260505-0
summary:
Silicone hydrophobic powder (SHP), is a versatile chemical additive known for its remarkable water-repellent properties. It is a fine, white powder composed of silicone polymer, a synthetic polymer known for its unique combination of flexibility, stability, and resistance to various environmental factors. == Chemistry == Commercially available siliconates include potassium methyl siliconate (CAS 31795-24-1, CH5KO3Si) and sodium methyl siliconate (CAS 16589-43-8, CH5NaO3Si). These are supplied as a concentrate in water with an active content of between 30% and 40% by weight. This solution is further diluted in water prior to their application by spraying, dipping or rolling to a mineral building material, such as brickwork, to make the surface water-repellent. The dilution is clear and stable with a high pH of 13 to 14. When applied to a surface, the siliconate reacts with carbon dioxide in the air to form an insoluble water-resistant treatment within 24 hours. CH5KO3Si + silanol functional substrate OHSi → CH4O3Si + KOH The methyl group has now attached itself to the substrata. 2KOH + CO2 → K2CO3 + H2O The salts formed by this reaction are often the cause of white efflorescence when too much of the solution is applied to the surface. == Types


id: hygroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Hygroscopy-0.md
category: reference
title: Hygroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hygroscopy
date_saved: 2026-05-05T10:52:41.014796+00:00
instance: kb-cron
parent: hygroscopy-20260505-0
summary:
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance's molecules, adsorbing substances can become physically changed, e.g. changing in volume, boiling point, viscosity or some other physical characteristic or property of the substance. For example, a finely dispersed hygroscopic powder, such as a salt, may become clumpy over time due to collection of moisture from the surrounding environment. Deliquescent materials are sufficiently hygroscopic that they dissolve in the water they absorb, forming an aqueous solution. Hygroscopy is essential for many plant and animal species' attainment of hydration, nutrition, reproduction and/or seed dispersal. Biological evolution created hygroscopic solutions for water harvesting, filament tensile strength, bonding and passive motion – natural solutions being considered in future biomimetics. == Etymology and pronunciation == The word hygroscopy () uses combining forms of hygro- (for moisture or humidity) and -scopy (observation). Originally, the word hygroscope referred to devices for measuring humidity level by visual observation. Early hygroscopes (circa 1790s) used materials such as certain animal hairs that visibly changed shape and size when they became damp. Such materials were


id: hygroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Hygroscopy-1.md
category: reference
title: Hygroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hygroscopy
date_saved: 2026-05-05T10:52:41.014796+00:00
instance: kb-cron
parent: hygroscopy-20260505-0
summary:
== Biology == Hygroscopy appears in both plant and animal kingdoms, the latter benefiting via hydration and nutrition. Some amphibian species secrete a hygroscopic mucus that harvests moisture from the air. Orb web building spiders produce hygroscopic secretions that preserve the stickiness and adhesion force of their webs. One aquatic reptile species is able to travel beyond aquatic limitations, onto land, due to its hygroscopic integument. Plants benefit from hygroscopy via hydration and reproduction – demonstrated by convergent evolution examples. Hygroscopic movement (hygrometrically activated movement) is integral in fertilization, seed/spore release, dispersal and germination. The phrase "hygroscopic movement" originated in 1904's "Vorlesungen Über Pflanzenphysiologie", translated in 1907 as "Lectures on Plant Physiology" (Ludwig Jost and R.J. Harvey Gibson, Oxford, 1907). When movement becomes larger scale, affected plant tissues are colloquially termed hygromorphs. Hygromorphy is a common mechanism of seed dispersal as the movement of dead tissues respond to hygrometric variation, e.g. spore release from the fertile margins of Onoclea sensibilis. Movement occurs when plant tissue matures, dies and desiccates, cell walls drying, shrinking; and also when humidity re-hydrates plant tissue, cell walls enlarging, expanding. The direction of the resulting force depends upon the architecture of the tissue and is capable


id: hygroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Hygroscopy-2.md
category: reference
title: Hygroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hygroscopy
date_saved: 2026-05-05T10:52:41.014796+00:00
instance: kb-cron
parent: hygroscopy-20260505-0
summary:
Hygroscopic bi-layered cell arrays act as a capitulum hinge in some plants, Xerochrysum bracteatum and Syngonanthus elegans being examples. The hygroscopic bending of involucral bracts surrounding a capitulum contributes to flower protection and pollination and assists dispersion by protecting delicate pappi filaments from entanglement or destruction by precipitation, e.g. Taraxacum (dandelions). In nature these involucral bracts have a diurnal rhythm. The whorl of hygroscopic bracts bend outward exposing the capitulum (see illustration) during the day, then inward, closing it at night, as the relative humidity shifts in response to the daily temperature change. Bracts are scarious, the hinge and blade composed exclusively of dead cells (Nishikawa et al., 2008), allowing the hygroscopically activated bracts to function from flowering through achene dispersal. Physiologically, the bract's lower section is source to the hinge-like function, consisting of sclerenchyma-like abaxial (inner petal) tissue, parenchyma and adaxial epidermis (outer petal tissue). Bract cell wall composition is rather uniform but its cells gradually change in orientation. The bract's hygroscopic bending is due to the differing cell orientations of its inner and outer epidermides, causing adaxial–abaxial force gradients between opposing sides that change with moisture; thus, the aggregate hygrometric force, in whorl unison, controls the capitulum's repetitive


id: hygroscopy-20260505-3
file: data/en.wikipedia.org/wiki/Hygroscopy-3.md
category: reference
title: Hygroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hygroscopy
date_saved: 2026-05-05T10:52:41.014796+00:00
instance: kb-cron
parent: hygroscopy-20260505-0
summary:
Two angiospermae families have similar methods of dispersal, though method of implementation varies within family: Geraniaceae family examples are the common stork's-bill (Erodium cicutarium) and geraniums (Pelargonium sp.); Poaceae family, Needle-and-Thread (Hesperostipa comata) and wheat (Triticum spp.). All rely upon a bi-layered parallel fiber hygroscopic cell physiology to control the awn's movement for dispersal and self-burial of seeds. Alignment of cellulose fibrils in the awn's controlling cell wall determines direction of movement. If fiber alignments are tilted, non-parallel venation, a helix develops and awn movement becomes twisting (coiling) instead of bending; e.g. coiling occurs in awns of Erodium, and Hesperostipa.


id: hygroscopy-20260505-4
file: data/en.wikipedia.org/wiki/Hygroscopy-4.md
category: reference
title: Hygroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Hygroscopy
date_saved: 2026-05-05T10:52:41.014796+00:00
instance: kb-cron
parent: hygroscopy-20260505-0
summary:
Some plants use hygroscopic movements for Ballochory (self-dispersal), active ballists forcibly ejecting their seeds; e.g. species of geranium, violet, wood sorrel, witch hazel, touch-me-not (Impatiens), and acanthus. Rupturing of the Bauhinia purpurea seed pod reportedly propels its seed up to 15 metres distance. == Engineering properties == Hygroscopicity is a general term used to describe a material's ability to absorb moisture from the environment. There is no standard quantitative definition of hygroscopicity, so generally the qualification of hygroscopic and non-hygroscopic is determined on a case-by-case basis. For example, pharmaceuticals that pick up more than 5% by mass, between 40 and 90% relative humidity at 25 °C, are described as hygroscopic, while materials that pick up less than 1%, under the same conditions are regarded as non-hygroscopic. The amount of moisture held by hygroscopic materials is usually proportional to the relative humidity. Tables containing this information can be found in many engineering handbooks and is also available from suppliers of various materials and chemicals. Hygroscopy also plays an important role in the engineering of plastic materials. Some plastics, e. g. nylon, are hygroscopic while others are not. == Polymers == Many engineering polymers are hygroscopic, including nylon, ABS, polycarbonate, cellulose, carboxymethyl


id: ionic-potential-20260505-0
file: data/en.wikipedia.org/wiki/Ionic_potential-0.md
category: reference
title: Ionic potential
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ionic_potential
date_saved: 2026-05-05T10:52:42.229974+00:00
instance: kb-cron
parent: ionic-potential-20260505-0
summary:
Ionic potential is the ratio of the electrical charge (z) to the radius (r) of an ion. Ionic potential = electrical charge ionic radius = z r {\displaystyle {\text{Ionic potential}}={\frac {\text{electrical charge}}{\text{ionic radius}}}={\frac {z}{r}}} As such, this ratio is a measure of the charge density at the surface of the ion; usually the denser the charge, the stronger the bond formed by the ion with ions of opposite charge. The ionic potential gives an indication of how strongly, or weakly, the ion will be electrostatically attracted by ions of opposite charge; and to what extent the ion will be repelled by ions of the same charge. Victor Moritz Goldschmidt, the father of modern geochemistry found that the behavior of an element in its environment could be predicted from its ionic potential and illustrated this with a diagram (plot of the bare ionic radius as a function of the ionic charge). For instance, the solubility of dissolved iron is highly dependent on its redox state. Fe2+ with a lower ionic potential than Fe3+ is much more soluble because it exerts a weaker interaction force with OH− ion present in water and exhibits a less pronounced trend to hydrolysis and precipitation. Under


id: ionization-energy-20260505-0
file: data/en.wikipedia.org/wiki/Ionization_energy-0.md
category: reference
title: Ionization energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ionization_energy
date_saved: 2026-05-05T10:52:43.455903+00:00
instance: kb-cron
parent: ionization-energy-20260505-0
summary:
In physics and chemistry, ionization energy (IE) is the minimum energy required to remove the most loosely bound electron(s) (the valence electron(s)) of an isolated gaseous atom, positive ion, or molecule. The first ionization energy is quantitatively expressed as X(g) + energy ⟶ X+(g) + e− where X is any atom or molecule, X+ is the resultant ion when the original atom was stripped of a single electron, and e− is the removed electron. Ionization energy is positive for neutral atoms, meaning that the ionization is an endothermic process. Roughly speaking, the closer the outermost electrons are to the nucleus of the atom, the higher the atom's ionization energy. In physics, ionization energy (IE) is usually expressed in electronvolts (eV) or joules (J). In chemistry, it is expressed as the energy to ionize a mole of atoms or molecules, usually as kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol). Comparison of ionization energies of atoms in the periodic table reveals two periodic trends which follow the rules of Coulombic attraction: Ionization energy generally increases from left to right within a given period (that is, row). Ionization energy generally decreases from top to bottom in a given group (that is,


id: ionization-energy-20260505-1
file: data/en.wikipedia.org/wiki/Ionization_energy-1.md
category: reference
title: Ionization energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ionization_energy
date_saved: 2026-05-05T10:52:43.455903+00:00
instance: kb-cron
parent: ionization-energy-20260505-0
summary:
== Atoms: values and trends == Generally, the (N+1)th ionization energy of a particular element is larger than the Nth ionization energy (it may also be noted that the ionization energy of an anion is generally less than that of cations and neutral atom for the same element). When the next ionization energy involves removing an electron from the same electron shell, the increase in ionization energy is primarily due to the increased net charge of the ion from which the electron is being removed. Electrons removed from more highly charged ions experience greater forces of electrostatic attraction; thus, their removal requires more energy. In addition, when the next ionization energy involves removing an electron from a lower electron shell, the greatly decreased distance between the nucleus and the electron also increases both the electrostatic force and the distance over which that force must be overcome to remove the electron. Both of these factors further increase the ionization energy. Some values for elements of the third period are given in the following table: Large jumps in the successive molar ionization energies occur when passing noble gas configurations. For example, as can be seen in the table above, the first two


id: ionization-energy-20260505-2
file: data/en.wikipedia.org/wiki/Ionization_energy-2.md
category: reference
title: Ionization energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ionization_energy
date_saved: 2026-05-05T10:52:43.455903+00:00
instance: kb-cron
parent: ionization-energy-20260505-0
summary:
==== Ionization energy decreases when ==== Transitioning to a new period: an alkali metal easily loses one electron to leave an octet or pseudo-noble gas configuration, so those elements have only small values for IE. Moving from the s-block to the p-block: a p-orbital loses an electron more easily. An example is beryllium to boron, with electron configuration 1s2 2s2 2p1. The 2s electrons shield the higher-energy 2p electron from the nucleus, making it slightly easier to remove. This also happens from magnesium to aluminium. Occupying a p-subshell with its first electron with spin opposed to the other electrons: such as in nitrogen ( 7N: 14.5 eV) to oxygen ( 8O: 13.6 eV), as well as phosphorus ( 15P: 10.48 eV) to sulfur ( 16S: 10.36 eV). The reason for this is because oxygen, sulfur and selenium all have dipping ionization energies because of shielding effects. However, this discontinues starting from tellurium where the shielding is too small to produce a dip. Moving from the d-block to the p-block: as in the case of zinc ( 30Zn: 9.4 eV) to gallium ( 31Ga: 6.0 eV) Special case: decrease from lead ( 82Pb: 7.42 eV) to bismuth ( 83Bi: 7.29 eV).


id: ionization-energy-20260505-3
file: data/en.wikipedia.org/wiki/Ionization_energy-3.md
category: reference
title: Ionization energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ionization_energy
date_saved: 2026-05-05T10:52:43.455903+00:00
instance: kb-cron
parent: ionization-energy-20260505-0
summary:
==== Ionization energy increases when ==== Reaching Group 18 noble gas elements: This is due to their complete electron subshells, so that these elements require large amounts of energy to remove one electron. Group 12: The elements here, zinc ( 30Zn: 9.4 eV), cadmium ( 48Cd: 9.0 eV) and mercury ( 80Hg: 10.4 eV) all record sudden rising IE values in contrast to their preceding elements: copper ( 29Cu: 7.7 eV), silver ( 47Ag: 7.6 eV) and gold ( 79Au: 9.2 eV), respectively. For mercury, it can be extrapolated that the relativistic stabilization of the 6s electrons increases the ionization energy, in addition to poor shielding by 4f electrons that increases the effective nuclear charge on the outer valence electrons. In addition, the closed-subshells electron configurations: [Ar] 3d10 4s2, [Kr] 4d105s2 and [Xe] 4f14 5d10 6s2 provide increased stability. Special case: shift from rhodium ( 45Rh: 7.5 eV) to palladium ( 46Pd: 8.3 eV). Unlike other Group 10 elements, palladium has a higher ionization energy than the preceding atom, due to its electron configuration. In contrast to nickel's [Ar] 3d8 4s2, and platinum's [Xe] 4f14 5d9 6s1, palladium's electron configuration is [Kr] 4d10 5s0 (even though the Madelung rule predicts


id: ionization-energy-20260505-4
file: data/en.wikipedia.org/wiki/Ionization_energy-4.md
category: reference
title: Ionization energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ionization_energy
date_saved: 2026-05-05T10:52:43.455903+00:00
instance: kb-cron
parent: ionization-energy-20260505-0
summary:
Group 1: Hydrogen's ionization energy is very high (at 13.59844 eV), compared to the alkali metals. This is due to its single electron (and hence, very small electron cloud), which is close to the nucleus. Likewise, since there are not any other electrons that may cause shielding, that single electron experiences the full net positive charge of the nucleus. Francium's ionization energy is higher than the precedent alkali metal, cesium. This is due to its (and radium's) small ionic radii owing to relativistic effects. Because of their large mass and size, this means that its electrons are traveling at extremely high speeds, which results in the electrons coming closer to the nucleus than expected, and they are consequently harder to remove (higher IE). Group 2: Radium's ionization energy is higher than its antecedent alkaline earth metal barium, like francium, which is also due to relativistic effects. The electrons, especially the 1s electrons, experience very high effective nuclear charges. To avoid falling into the nucleus, the 1s electrons must move at very high speeds, which causes the special relativistic corrections to be substantially higher than the approximate classical momenta. By the uncertainty principle, this causes a relativistic contraction of the 1s


id: ionization-energy-20260505-5
file: data/en.wikipedia.org/wiki/Ionization_energy-5.md
category: reference
title: Ionization energy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ionization_energy
date_saved: 2026-05-05T10:52:43.455903+00:00
instance: kb-cron
parent: ionization-energy-20260505-0
summary:
According to the more complete theory of quantum mechanics, the location of an electron is best described as a probability distribution within an electron cloud, i.e. atomic orbital. The energy can be calculated by integrating over this cloud. The cloud's underlying mathematical representation is the wavefunction, which is built from Slater determinants consisting of molecular spin orbitals. These are related by Pauli's exclusion principle to the antisymmetrized products of the atomic or molecular orbitals. There are two main ways in which ionization energy is calculated. In general, the computation for the Nth ionization energy requires calculating the energies of Z − N + 1 {\displaystyle Z-N+1} and Z − N {\displaystyle Z-N} electron systems. Calculating these energies exactly is not possible except for the simplest systems (i.e. hydrogen and hydrogen-like elements), primarily because of difficulties in integrating the electron correlation terms. Therefore, approximation methods are routinely employed, with different methods varying in complexity (computational time) and accuracy compared to empirical data. This has become a well-studied problem and is routinely done in computational chemistry. The second way of calculating ionization energies is mainly used at the lowest level of approximation, where the ionization energy is provided by Koopmans' theorem, which


id: kosmotropic-20260505-0
file: data/en.wikipedia.org/wiki/Kosmotropic-0.md
category: reference
title: Kosmotropic
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Kosmotropic
date_saved: 2026-05-05T10:52:44.615216+00:00
instance: kb-cron
parent: kosmotropic-20260505-0
summary:
Co-solvents (in water solvent) are defined as kosmotropic (order-making) if they contribute to the stability and structure of water-water interactions. In contrast, chaotropic (disorder-making) agents have the opposite effect, disrupting water structure, increasing the solubility of nonpolar solvent particles, and destabilizing solute aggregates. Kosmotropes cause water molecules to favorably interact, which in effect stabilizes intramolecular interactions in macromolecules such as proteins. == Ionic kosmotropes == Ionic kosmotropes tend to be small or have high charge density. Some ionic kosmotropes are CO2−3, SO2−4, HPO2−4, Mg2+, Li+, Zn2+ and Al3+. Large ions or ions with low charge density (such as Br−, I−, K+, Cs+) instead act as chaotropes. Kosmotropic anions are more polarizable and hydrate more strongly than kosmotropic cations of the same charge density. A scale can be established if one refers to the Hofmeister series or looks up the free energy of hydrogen bonding ( Δ G H B {\displaystyle \Delta G_{\rm {HB}}} ) of the salts, which quantifies the extent of hydrogen bonding of an ion in water. For example, the kosmotropes CO2−3 and OH− have Δ G H B {\displaystyle \Delta G_{\rm {HB}}} between 0.1 and 0.4 J/mol, whereas the chaotrope SCN− has a Δ G H B


id: kr-ger-vink-notation-20260505-0
file: data/en.wikipedia.org/wiki/Kröger–Vink_notation-0.md
category: reference
title: Kröger–Vink notation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Kröger–Vink_notation
date_saved: 2026-05-05T10:52:45.820266+00:00
instance: kb-cron
parent: kr-ger-vink-notation-20260505-0
summary:
Kröger–Vink notation is a set of conventions that are used to describe electric charges and lattice positions of point defect species in crystals. It is primarily used for ionic crystals and is particularly useful for describing various defect reactions. It was proposed by Ferdinand Anne Kröger and Hendrik Jan Vink. == Notation == The notation follows the scheme: MCS M corresponds to the species. These can be atoms – e.g., Si, Ni, O, Cl vacancies – V or v (since V is also the symbol for vanadium) interstitials – i (although this is usually used to describe lattice site, not species) electrons – e electron holes – h S indicates the lattice site that the species occupies. For instance, Ni might occupy a Cu site. In this case, M would be replaced by Ni and S would be replaced by Cu. The site may also be a lattice interstice, in this case, the symbol "i" is used. A cation site can be represented by the symbols C or M (for metal), and an anion site can be represented by either an A or X. C corresponds to the electronic charge of the species relative to the site that it occupies.


id: kr-ger-vink-notation-20260505-1
file: data/en.wikipedia.org/wiki/Kröger–Vink_notation-1.md
category: reference
title: Kröger–Vink notation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Kröger–Vink_notation
date_saved: 2026-05-05T10:52:45.820266+00:00
instance: kb-cron
parent: kr-ger-vink-notation-20260505-0
summary:
== Oxidation–reduction tree == The following oxidation–reduction tree for a simple ionic compound, AX, where A is a cation and X is an anion, summarizes the various ways in which intrinsic defects can form. Depending on the cation-to-anion ratio, the species can either be reduced and therefore classified as n-type, or if the converse is true, the ionic species is classified as p-type. Below, the tree is shown for a further explanation of the pathways and results of each breakdown of the substance. === Schematic examples === From the chart above, there are total of four possible chemical reactions using Kröger–Vink Notation depending on the intrinsic deficiency of atoms within the material. Assume the chemical composition is AX, with A being the cation and X being the anion. (The following assumes that X is a diatomic gas such as oxygen and therefore cation A has a +2 charge. Note that materials with this defect structure are often used in oxygen sensors.) In the reduced n-type, there are excess cations on the interstitial sites: A×A + X×X ⇌ A••i + 1⁄2 X2(g) + 2 e⁠ ′ {\displaystyle \prime } ⁠ In the reduced n-type, there is a deficiency of anions on


id: lipophilicity-20260505-0
file: data/en.wikipedia.org/wiki/Lipophilicity-0.md
category: reference
title: Lipophilicity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lipophilicity
date_saved: 2026-05-05T10:52:46.996407+00:00
instance: kb-cron
parent: lipophilicity-20260505-0
summary:
Lipophilicity (from Greek λίπος "fat" and φίλος "friendly") is the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such compounds are called lipophilic (translated as "fat-loving" or "fat-liking"). Such non-polar solvents are themselves lipophilic, and the adage "like dissolves like" generally holds true. Thus lipophilic substances tend to dissolve in other lipophilic substances, whereas hydrophilic ("water-loving") substances tend to dissolve in water and other hydrophilic substances. Lipophilicity, hydrophobicity, and non-polarity may describe the same tendency towards participation in the London dispersion force, as the terms are often used interchangeably. However, the terms "lipophilic" and "hydrophobic" are not synonymous, as can be seen with silicones and fluorocarbons, which are hydrophobic but not lipophilic. == Surfactants == Hydrocarbon-based surfactants are compounds that are amphiphilic (or amphipathic), having a hydrophilic, water interactive "end", referred to as their "head group", and a lipophilic "end", usually a long chain hydrocarbon fragment, referred to as their "tail". They congregate at low energy surfaces, including the air-water interface (lowering surface tension) and the surfaces of the water-immiscible droplets found in oil/water emulsions (lowering interfacial tension). At these surfaces they naturally orient themselves with their head groups


id: lipophobicity-20260505-0
file: data/en.wikipedia.org/wiki/Lipophobicity-0.md
category: reference
title: Lipophobicity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lipophobicity
date_saved: 2026-05-05T10:52:48.216308+00:00
instance: kb-cron
parent: lipophobicity-20260505-0
summary:
Lipophobicity, also sometimes called lipophobia (from the Greek λιποφοβία from λίπος lipos "fat" and φόβος phobos "fear"), is a chemical property of chemical compounds which means "fat rejection", literally "fear of fat". Lipophobic compounds are those not soluble in lipids or other non-polar solvents. From the other point of view, they do not absorb fats. "Oleophobic" (from the Latin oleum "oil", Greek ελαιοφοβικό eleophobico from έλαιο eleo "oil" and φόβος phobos "fear") refers to the physical property of a molecule that is seemingly repelled from oil. (Strictly speaking, there is no repulsive force involved; it is an absence of attraction.) The most common lipophobic substance is water. Fluorocarbons are also lipophobic/oleophobic in addition to being hydrophobic. == Uses == A lipophobic coating has been used on the touchscreens of Apple's iPhones since the 3GS, their iPads, Nokia's N9 and Lumia devices, the HTC HD2, the Blackberry DTEK50, Hero, and Flyer and many other phones to repel fingerprint oil, which aids in preventing and cleaning fingerprint marks. Most "oleophobic" coatings used on mobile devices are fluoropolymer-based solids (similar to Teflon, which was used on the HTC Hero) and are both lipophobic and hydrophobic. The oleophobic coating beads up the oils left


id: list-of-materials-properties-20260505-0
file: data/en.wikipedia.org/wiki/List_of_materials_properties-0.md
category: reference
title: List of materials properties
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_materials_properties
date_saved: 2026-05-05T10:52:49.367032+00:00
instance: kb-cron
parent: list-of-materials-properties-20260505-0
summary:
A material property is an intensive property of a material, i.e., a physical property or chemical property that does not depend on the amount of the material. These quantitative properties may be used as a metric by which the benefits of one material versus another can be compared, thereby aiding in materials selection. A property having a fixed value for a given material or substance is called material constant or constant of matter. (Material constants should not be confused with physical constants, that have a universal character.) A material property may also be a function of one or more independent variables, such as temperature. Materials properties often vary to some degree according to the direction in the material in which they are measured, a condition referred to as anisotropy. Materials properties that relate to different physical phenomena often behave linearly (or approximately so) in a given operating range . Modeling them as linear functions can significantly simplify the differential constitutive equations that are used to describe the property. Equations describing relevant materials properties are often used to predict the attributes of a system. The properties are measured by standardized test methods. Many such methods have been documented by their respective


id: lnapl-transmissivity-20260505-0
file: data/en.wikipedia.org/wiki/LNAPL_transmissivity-0.md
category: reference
title: LNAPL transmissivity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/LNAPL_transmissivity
date_saved: 2026-05-05T10:52:50.570687+00:00
instance: kb-cron
parent: lnapl-transmissivity-20260505-0
summary:
LNAPL transmissivity is the discharge of light non-aqueous phase liquid (LNAPL) through a unit width of aquifer for a unit gradient. Scholars Alex Mayer and S. Majid Hassanizadeh define LNAPL transmissivity as the "product of the porous medium permeability and the LNAPL relative permeability, which in turn is a function of saturation, and the thickness of the LNAPL". They wrote that once LNAPL is taken away, a lower recovery rate occurs because the "saturation and thickness of the mobile LNAPL fraction decreases". LNAPL transmissivity is a summary parameter that takes into account soil type and physical properties (e.g., porosity and permeability), LNAPL physical fluid properties(e.g., density and viscosity) and LNAPL saturation (i.e., amount of LNAPL present within the pore network). Consequently, LNAPL transmissivity is comparable across soil types, LNAPL types and recoverable LNAPL volumes. More importantly, for LNAPL recovery from a given well, the soil and LNAPL physical properties do not change significantly through time. What changes, is the LNAPL saturation (amount of LNAPL present). As a result, LNAPL transmissivity decreases in direct proportion to the decrease in LNAPL saturation achievable through liquid recovery technology. LNAPL Transmissivity is not the only piece of data required when evaluating a site overall,


id: lower-flammability-limit-20260505-0
file: data/en.wikipedia.org/wiki/Lower_flammability_limit-0.md
category: reference
title: Lower flammability limit
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lower_flammability_limit
date_saved: 2026-05-05T10:52:51.783771+00:00
instance: kb-cron
parent: lower-flammability-limit-20260505-0
summary:
The lower flammability limit (LFL), usually expressed in volume per cent, is the lower end of the concentration range over which a flammable mixture of gas or vapour in air can be ignited at a given temperature and pressure. The flammability range is delineated by the upper and lower flammability limits. Outside this range of air/vapor mixtures, the mixture cannot be ignited at that temperature and pressure. The LFL decreases with increasing temperature; thus, a mixture that is below its LFL at a given temperature may be ignitable if heated sufficiently. For liquids, the LFL is typically close to the saturated vapor concentration at the flash point, however, due to differences in the liquid properties, the relationship of LFL to flash point (which is also dependent on the test apparatus) is not fixed and some spread in the data usually exists. The L F L m i x {\displaystyle LFL_{mix}} of a mixture can be evaluated using the Le Chatelier mixing rule if the L F L i {\displaystyle LFL_{i}} of the components i {\displaystyle i} are known: L F L m i x = 1 ∑ x i L F L i {\displaystyle LFL_{mix}={\frac {1}{\sum {\frac {x_{i}}{LFL_{i}}}}}} Where L


id: lyotropic-liquid-crystal-20260505-0
file: data/en.wikipedia.org/wiki/Lyotropic_liquid_crystal-0.md
category: reference
title: Lyotropic liquid crystal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lyotropic_liquid_crystal
date_saved: 2026-05-05T10:52:52.958334+00:00
instance: kb-cron
parent: lyotropic-liquid-crystal-20260505-0
summary:
Lyotropic liquid crystals result when amphiphiles, which are both hydrophobic and hydrophilic, dissolve into a solution that behaves both like a liquid and a solid crystal. This liquid crystalline mesophase includes everyday mixtures like soap and water. The term lyotropic comes from Ancient Greek λύω (lúō) 'to dissolve' and τροπικός (tropikós) 'change'. Historically, the term was used to describe the common behavior of materials composed of amphiphilic molecules upon the addition of a solvent. Such molecules comprise a hydrophilic (literally 'water-loving') head-group (which may be ionic or non-ionic) attached to a hydrophobic ('water-hating') group. The micro-phase segregation of two incompatible components on a nanometer scale results in different types of solvent-induced extended anisotropic arrangement, depending on the volume balances between the hydrophilic part and hydrophobic part. In turn, they generate the long-range order of the phases, with the solvent molecules filling the space around the compounds to provide fluidity to the system. In contrast to thermotropic liquid crystals, lyotropic liquid crystals have therefore an additional degree of freedom, that is the concentration that enables them to induce a variety of different phases. As the concentration of amphiphilic molecules is increased, several different type of lyotropic liquid crystal structures occur in


id: lyotropic-liquid-crystal-20260505-1
file: data/en.wikipedia.org/wiki/Lyotropic_liquid_crystal-1.md
category: reference
title: Lyotropic liquid crystal
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Lyotropic_liquid_crystal
date_saved: 2026-05-05T10:52:52.958334+00:00
instance: kb-cron
parent: lyotropic-liquid-crystal-20260505-0
summary:
== Host molecules == It is possible that specific molecules are dissolved in lyotropic mesophases, where they can be located mainly inside, outside, or at the surface of the aggregates. Some of such molecules act as dopants, inducing specific properties to the whole phase, other ones can be considered simple guests with limited effect on the surrounding environment but possibly strong consequences on their physico-chemical properties, and some of them are used as probe to detect molecular-level properties of the whole mesophase in specific analytical techniques. === Rod-like macromolecules === The term lyotropic has also been applied to the liquid crystalline phases that are formed by certain polymeric materials, particularly those consisting of rigid rod-like macromolecules, when they are mixed with appropriate solvents. Examples are suspensions of rod-like viruses such as the tobacco mosaic virus as well as synthetic macromolecules, such as Li2Mo6Se6 nanowire or colloidal suspensions of non-spherical colloidal particles. Cellulose and cellulose derivatives form lyotropic liquid crystal phases as do nanocrystalline (nanocellulose) suspensions. Other examples include DNA and Kevlar, which dissolve in sulfuric acid to give a lyotropic phase. It is noted that in these cases the solvent acts to lower the melting point of the materials thereby


id: mass-number-20260505-0
file: data/en.wikipedia.org/wiki/Mass_number-0.md
category: reference
title: Mass number
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_number
date_saved: 2026-05-05T10:52:54.133778+00:00
instance: kb-cron
parent: mass-number-20260505-0
summary:
The mass number (symbol A, from the German word: Atomgewicht, "atomic weight"), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approximately equal to the atomic (also known as isotopic) mass of the atom expressed in daltons. Since protons and neutrons are both baryons, the mass number A is identical with the baryon number B of the nucleus (and also of the whole atom or ion). The mass number is different for each isotope of a given chemical element, and the difference between the mass number and the atomic number Z gives the number of neutrons (N) in the nucleus: N = A − Z. The mass number is written either after the element name or as a superscript to the left of an element's symbol. For example, the most common isotope of carbon is carbon-12, or 12C, which has 6 protons and 6 neutrons. The full isotope symbol would also have the atomic number (Z) as a subscript to the left of the element symbol directly below the mass number: 126C. == Mass number changes in radioactive decay == Different types of


id: mass-flux-fraction-20260505-0
file: data/en.wikipedia.org/wiki/Mass-flux_fraction-0.md
category: reference
title: Mass-flux fraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass-flux_fraction
date_saved: 2026-05-05T10:52:55.320426+00:00
instance: kb-cron
parent: mass-flux-fraction-20260505-0
summary:
The mass-flux fraction (or Hirschfelder-Curtiss variable or Kármán-Penner variable) is the ratio of mass-flux of a particular chemical species to the total mass flux of a gaseous mixture. It includes both the convectional mass flux and the diffusional mass flux. It was introduced by Joseph O. Hirschfelder and Charles F. Curtiss in 1948 and later by Theodore von Kármán and Sol Penner in 1954. The mass-flux fraction of a species i is defined as ϵ i = ρ i ( v + V i ) ρ v = Y i ( 1 + V i v ) {\displaystyle \epsilon _{i}={\frac {\rho _{i}(v+V_{i})}{\rho v}}=Y_{i}\left(1+{\frac {V_{i}}{v}}\right)} where Y i = ρ i / ρ {\displaystyle Y_{i}=\rho _{i}/\rho } is the mass fraction v {\displaystyle v} is the mass average velocity of the gaseous mixture V i {\displaystyle V_{i}} is the average velocity with which the species i diffuse relative to v {\displaystyle v} ρ i {\displaystyle \rho _{i}} is the density of species i ρ {\displaystyle \rho } is the gas density. It satisfies the identity ∑ i ϵ i = 1 {\displaystyle \sum _{i}\epsilon _{i}=1} , similar to the mass fraction, but the mass-flux fraction can take both positive and negative


id: metastability-20260505-0
file: data/en.wikipedia.org/wiki/Metastability-0.md
category: reference
title: Metastability
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Metastability
date_saved: 2026-05-05T10:52:56.509242+00:00
instance: kb-cron
parent: metastability-20260505-0
summary:
In chemistry and physics, metastability is an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball is only slightly pushed, it will settle back into its hollow, but a stronger push may start the ball rolling down the slope. Bowling pins show similar metastability by either merely wobbling for a moment or tipping over completely. A common example of metastability in science is isomerisation. Higher energy isomers are long lived because they are prevented from rearranging to their preferred ground state by (possibly large) barriers in the potential energy. During a metastable state of finite lifetime, all state-describing parameters reach and hold stationary values. In isolation: the state of least energy is the only one the system will inhabit for an indefinite length of time, until more external energy is added to the system (unique "absolutely stable" state); the system will spontaneously leave any other state (of higher energy) to eventually return (after a sequence of transitions) to the least energetic state. The metastability concept originated in the physics of first-order phase transitions. It then acquired


id: metastability-20260505-1
file: data/en.wikipedia.org/wiki/Metastability-1.md
category: reference
title: Metastability
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Metastability
date_saved: 2026-05-05T10:52:56.509242+00:00
instance: kb-cron
parent: metastability-20260505-0
summary:
== Quantum mechanics == Aggregated systems of subatomic particles described by quantum mechanics (quarks inside nucleons, nucleons inside atomic nuclei, electrons inside atoms, molecules, or atomic clusters) are found to have many distinguishable states. Of these, one (or a small degenerate set) is indefinitely stable: the ground state or global minimum. All other states besides the ground state (or those degenerate with it) have higher energies. Of all these other states, the metastable states are the ones having lifetimes lasting at least 102 to 103 times longer than the shortest lived states of the set. A metastable state is then long-lived (locally stable with respect to configurations of 'neighbouring' energies) but not eternal (as the global minimum is). Being excited – of an energy above the ground state – it will eventually decay to a more stable state, releasing energy. Indeed, above absolute zero, all states of a system have a non-zero probability to decay; that is, to spontaneously fall into another state (usually lower in energy). One mechanism for this to happen is through tunnelling. === Nuclear physics === Some energetic states of an atomic nucleus (having distinct spatial mass, charge, spin, isospin distributions) are much longer-lived than others


id: miscibility-20260505-0
file: data/en.wikipedia.org/wiki/Miscibility-0.md
category: reference
title: Miscibility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Miscibility
date_saved: 2026-05-05T10:52:57.705522+00:00
instance: kb-cron
parent: miscibility-20260505-0
summary:
Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration), forming a homogeneous mixture (a solution). Such substances are said to be miscible (etymologically equivalent to the common term "mixable"). The term is most often applied to liquids, but also applies to solids and gases. An example in liquids is the miscibility of water and ethanol as they mix in all proportions. By contrast, substances are said to be immiscible if the mixture does not form a solution for certain proportions. For one example, oil is not soluble in water, so these two solvents are immiscible. As another example, butanone (methyl ethyl ketone) is immiscible in water: it is soluble in water up to about 275 grams per liter, but will separate into two phases beyond that. == Organic compounds == In organic compounds, the weight percent of hydrocarbon chain often determines the compound's miscibility with water. For example, among the alcohols, ethanol has two carbon atoms and is miscible with water, whereas 1-butanol with four carbons is not. 1-Octanol, with eight carbons, is practically insoluble in water, and its immiscibility leads it to be used


id: mixing-ratio-20260505-0
file: data/en.wikipedia.org/wiki/Mixing_ratio-0.md
category: reference
title: Mixing ratio
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mixing_ratio
date_saved: 2026-05-05T10:52:58.959905+00:00
instance: kb-cron
parent: mixing-ratio-20260505-0
summary:
In chemistry and physics, the dimensionless mixing ratio is the abundance of one component of a mixture relative to that of all other components. The term can refer either to mole ratio (see concentration) or mass ratio (see stoichiometry). == In atmospheric chemistry and meteorology == === Mole ratio === In atmospheric chemistry, mixing ratio usually refers to the mole ratio ri, which is defined as the amount of a constituent ni divided by the total amount of all other constituents in a mixture: r i = n i n t o t − n i {\displaystyle r_{i}={\frac {n_{i}}{n_{\mathrm {tot} }-n_{i}}}} The mole ratio is also called amount ratio. If ni is much smaller than ntot (which is the case for atmospheric trace constituents), the mole ratio is almost identical to the mole fraction. === Mass ratio === In meteorology, mixing ratio usually refers to the mass ratio of water ζ {\displaystyle \zeta } , which is defined as the mass of water m H 2 O {\displaystyle m_{\mathrm {H2O} }} divided by the mass of dry air ( m a i r − m H 2 O {\displaystyle m_{\mathrm {air} }-m_{\mathrm {H2O} }} ) in a given air parcel:


id: molality-20260505-0
file: data/en.wikipedia.org/wiki/Molality-0.md
category: reference
title: Molality
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molality
date_saved: 2026-05-05T10:53:00.168033+00:00
instance: kb-cron
parent: molality-20260505-0
summary:
In chemistry, molality is a measure of the amount of solute in a solution relative to a given mass of solvent. This contrasts with the definition of molarity which is based on a given volume of solution. A commonly used unit for molality is moles of solute per kilogram solvent (mol/kg). A solution of concentration 1 mol/kg is often written as 1 molal (or 1 m). == Definition == The molality (b), of a solution is defined as the amount of substance (in moles) of solute, nsolute, divided by the mass (in kg) of the solvent, msolvent: b = n s o l u t e m s o l v e n t {\displaystyle b={\frac {n_{\mathrm {solute} }}{m_{\mathrm {solvent} }}}} . In the case of solutions with more than one solvent, molality can be defined for the mixed solvent considered as a pure pseudo-solvent. Instead of mole solute per kilogram solvent as in the binary case, units are defined as mole solute per kilogram mixed solvent. == Origin == The term molality is formed in analogy to molarity which is the molar concentration of a solution. The earliest known use of the intensive property molality and of its adjectival


id: molality-20260505-1
file: data/en.wikipedia.org/wiki/Molality-1.md
category: reference
title: Molality
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molality
date_saved: 2026-05-05T10:53:00.168033+00:00
instance: kb-cron
parent: molality-20260505-0
summary:
where b1 is the molality and M1 is the molar mass of the solute. More generally, for an n-solute/one-solvent solution, letting bi and wi be, respectively, the molality and mass fraction of the i-th solute, w i = w 0 b i M i , b i = w i w 0 M i {\displaystyle w_{i}=w_{0}b_{i}M_{i},\quad b_{i}={\frac {w_{i}}{w_{0}M_{i}}}} , where Mi is the molar mass of the ith solute, and w0 is the mass fraction of the solvent, which is expressible both as a function of the molalities as well as a function of the other mass fractions, w 0 = 1 1 + ∑ j = 1 n b j M j = 1 − ∑ j = 1 n w j {\displaystyle w_{0}={\frac {1}{1+\displaystyle \sum _{j=1}^{n}{b_{j}M_{j}}}}=1-\sum _{j=1}^{n}{w_{j}}} . Substitution gives: w i = b i M i 1 + ∑ j = 1 n b j M j , b i = w i ( 1 − ∑ j = 1 n w j ) M i {\displaystyle w_{i}={\frac {b_{i}M_{i}}{1+\displaystyle \sum _{j=1}^{n}b_{j}M_{j}}},\quad b_{i}={\frac {w_{i}}{\left(1-\displaystyle \sum _{j=1}^{n}w_{j}\right)M_{i}}}} . === Mole fraction === The conversions to and from the mole fraction, x1 mole fraction of the solute in a single-solute


id: molality-20260505-2
file: data/en.wikipedia.org/wiki/Molality-2.md
category: reference
title: Molality
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molality
date_saved: 2026-05-05T10:53:00.168033+00:00
instance: kb-cron
parent: molality-20260505-0
summary:
b i b j = x i x j = c i c j = ρ i M j ρ j M i = w i M j w j M i {\displaystyle {\frac {b_{i}}{b_{j}}}={\frac {x_{i}}{x_{j}}}={\frac {c_{i}}{c_{j}}}={\frac {\rho _{i}M_{j}}{\rho _{j}M_{i}}}={\frac {w_{i}M_{j}}{w_{j}M_{i}}}} , where i and j are subscripts representing all the constituents, the n solutes plus the solvent. === Example of conversion === An acid mixture consists of 0.76, 0.04, and 0.20 mass fractions of 70% HNO3, 49% HF, and H2O, where the percentages refer to mass fractions of the bottled acids carrying a balance of H2O. The first step is determining the mass fractions of the constituents: w H N O 3 = 0.70 × 0.76 = 0.532 w H F = 0.49 × 0.04 = 0.0196 w H 2 O = 1 − w H N O 3 − w H F = 0.448 {\displaystyle {\begin{aligned}w_{\mathrm {HNO_{3}} }&=0.70\times 0.76=0.532\\w_{\mathrm {HF} }&=0.49\times 0.04=0.0196\\w_{\mathrm {H_{2}O} }&=1-w_{\mathrm {HNO_{3}} }-w_{\mathrm {HF} }=0.448\\\end{aligned}}} . The approximate molar masses in kg/mol are M H N O 3 = 0.063 k g / m o l , M H F = 0.020 k g / m o l , M H 2 O = 0.018


id: molality-20260505-3
file: data/en.wikipedia.org/wiki/Molality-3.md
category: reference
title: Molality
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molality
date_saved: 2026-05-05T10:53:00.168033+00:00
instance: kb-cron
parent: molality-20260505-0
summary:
=== Relation to apparent molar properties and activity coefficients === For concentrated ionic solutions the activity coefficient of the electrolyte is split into electric and statistical components. The statistical part includes molality b, hydration index number h, the number of ions from the dissociation and the ratio ra between the apparent molar volume of the electrolyte and the molar volume of water. Concentrated solution statistical part of the activity coefficient is: ln ⁡ γ s = h − ν ν ln ⁡ ( 1 + b r a 55.5 ) − h ν ln ⁡ ( 1 − b r a 55.5 ) + b r a ( r a + h − ν ) 55.5 ( 1 + b r a 55.5 ) {\displaystyle \ln \gamma _{s}={\frac {h-\nu }{\nu }}\ln \left(1+{\frac {br_{a}}{55.5}}\right)-{\frac {h}{\nu }}\ln \left(1-{\frac {br_{a}}{55.5}}\right)+{\frac {br_{a}\left(r_{a}+h-\nu \right)}{55.5\left(1+{\frac {br_{a}}{55.5}}\right)}}} . == Molalities of a ternary or multicomponent solution == The molalities of solutes b1, b2 in a ternary solution obtained by mixing two binary aqueous solutions with different solutes (say a sugar and a salt or two different salts) are different than the initial molalities of the solutes bii in their binary solutions: b 1 = m 11 M


id: molality-20260505-4
file: data/en.wikipedia.org/wiki/Molality-4.md
category: reference
title: Molality
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molality
date_saved: 2026-05-05T10:53:00.168033+00:00
instance: kb-cron
parent: molality-20260505-0
summary:
b 1 = b 11 m 01 m 01 + m 02 = b 11 1 + m 02 m 01 = b 11 1 + m s 2 m s 1 1 + b 11 M 1 1 + b 22 M 2 {\displaystyle b_{1}={\frac {b_{11}m_{01}}{m_{01}+m_{02}}}={\frac {b_{11}}{1+{\frac {m_{02}}{m_{01}}}}}={\frac {b_{11}}{1+{\frac {m_{s2}}{m_{s1}}}{\frac {1+b_{11}M_{1}}{1+b_{22}M_{2}}}}}} , b 2 = b 22 m 02 m 01 + m 02 = b 22 1 + m 01 m 02 = b 22 1 + m s 1 m s 2 1 + b 22 M 2 1 + b 11 M 1 {\displaystyle b_{2}={\frac {b_{22}m_{02}}{m_{01}+m_{02}}}={\frac {b_{22}}{1+{\frac {m_{01}}{m_{02}}}}}={\frac {b_{22}}{1+{\frac {m_{s1}}{m_{s2}}}{\frac {1+b_{22}M_{2}}{1+b_{11}M_{1}}}}}} . For solutions with three or more solutes the denominator is a sum of the masses of solvent in the n binary solutions which are mixed: b 1 = m 11 M 1 ( m 01 + m 02 + m 03 + . . . ) = n 11 m 01 + m 02 + . . = b 11 1 + m 02 m 01 + m 03 m 01 + . . . {\displaystyle b_{1}={\frac {m_{11}}{M_{1}(m_{01}+m_{02}+m_{03}+...)}}={\frac {n_{11}}{m_{01}+m_{02}+..}}={\frac {b_{11}}{1+{\frac {m_{02}}{m_{01}}}+{\frac {m_{03}}{m_{01}}}+...}}} , b 2 = m 22 M 2 ( m 01 +


id: molar-mass-20260505-0
file: data/en.wikipedia.org/wiki/Molar_mass-0.md
category: reference
title: Molar mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molar_mass
date_saved: 2026-05-05T10:53:01.382556+00:00
instance: kb-cron
parent: molar-mass-20260505-0
summary:
In chemistry, the molar mass (M) (sometimes called molecular weight or formula weight, but see related quantities for usage) of a chemical substance (element or compound) is defined as the ratio between the mass (m) and the amount of substance (n, measured in moles) of any sample of the substance: M = m/n. The molar mass is a bulk, not molecular, property of a substance. The molar mass is a weighted average of many instances of the element or compound, which often vary in mass due to the presence of isotopes. Most commonly, the molar mass is computed from the standard atomic weights and is thus a terrestrial average and a function of the relative abundance of the isotopes of the constituent atoms on Earth. The molecular mass (for molecular compounds) and formula mass (for non-molecular compounds, such as ionic salts) are commonly used as synonyms of molar mass, as the numerical values are identical (for all practical purposes), differing only in units (dalton vs. g/mol or kg/kmol). However, the most authoritative sources define it differently. The difference is that molecular mass is the mass of one specific particle or molecule (a microscopic quantity), while the molar mass is an


id: molar-mass-20260505-1
file: data/en.wikipedia.org/wiki/Molar_mass-1.md
category: reference
title: Molar mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molar_mass
date_saved: 2026-05-05T10:53:01.382556+00:00
instance: kb-cron
parent: molar-mass-20260505-0
summary:
== Technical background == For a pure sample of a substance X, the known molar mass, M(X), is used for calculating the amount of the substance in the sample, n(X), given the mass of the sample, m(X), through the equation: n(X) = m(X)/M(X). If N(X) is the number of entities of the substance in the sample, and ma(X) is the mass of each entity of the substance (atomic mass, molecular mass, or formula mass), then the mass of the sample is m(X) = N(X) ⋅ ma(X), and the amount of substance is n(X) = N(X)/NA = N(X) ⋅ na, where na is the elementary amount, an amount consisting of exactly one atomic-scale entity of any kind (atom, molecule, formula unit), analogous to the elementary charge e. Since the elementary amount is the reciprocal of the Avogadro constant, using the relationship M(X) = m(X)/n(X), the molar mass is then given by M(X) = ma(X) ⋅ NA = ma(X)/na (dimension M/N), i.e. the atomic-scale mass of one entity of the substance per elementary amount. Given the relative atomic-scale mass (atomic weight, molecular weight, or formula weight) Ar(X) of an entity of a substance X, its mass expressed in daltons is ma(X) =


id: molar-mass-20260505-2
file: data/en.wikipedia.org/wiki/Molar_mass-2.md
category: reference
title: Molar mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molar_mass
date_saved: 2026-05-05T10:53:01.382556+00:00
instance: kb-cron
parent: molar-mass-20260505-0
summary:
The molar mass M(X) of a compound is given by the sum of the relative atomic masses Ar(Xi) of the elements (each multiplied by the number of atoms ni per element) which form the compound multiplied by the molar mass constant, Mu ≈ 1 g/mol: M ( X ) = M r ( X ) ⋅ M u = M u ∑ i n i A r ( X i ) . {\displaystyle M({\text{X}})=M_{\text{r}}({\text{X}})\cdot M_{\text{u}}=M_{\text{u}}\sum _{i}n_{i}A_{\text{r}}({\text{X}}_{i}).} Here, Mr(X) is the relative molar mass, also called molecular weight or formula weight. For normal samples from Earth with typical isotope composition, the standard atomic weight or the conventional atomic weight can be used as an approximation of the relative atomic mass of the sample. Examples are: M ( NaCl ) = [ 22.98976928 ( 2 ) + 35.453 ( 2 ) ] × M u = 58.443 ( 2 ) g/mol M ( C 12 H 22 O 11 ) = [ 12 × 12.0107 ( 8 ) + 22 × 1.00794 ( 7 ) + 11 × 15.9994 ( 3 ) ] × M u = 342.297 ( 14 ) g/mol {\displaystyle {\begin{array}{lll}M({\ce {NaCl}})&=[22.98976928(2)+35.453(2)]\times M_{\text{u}}\\&=58.443(2){\text{ g/mol}}\\M({\ce {C12H22O11}})&=[12\times 12.0107(8)+22\times 1.00794(7)+11\times 15.9994(3)]\times M_{\text{u}}\\&=342.297(14){\text{


id: molar-mass-20260505-3
file: data/en.wikipedia.org/wiki/Molar_mass-3.md
category: reference
title: Molar mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molar_mass
date_saved: 2026-05-05T10:53:01.382556+00:00
instance: kb-cron
parent: molar-mass-20260505-0
summary:
== Precision and uncertainties == The precision to which a molar mass is known depends on the precision of the atomic masses from which it was calculated (and very slightly on the value of the molar mass constant, which depends on the measured value of the dalton). Most atomic masses are known to a precision of at least one part in ten-thousand, often much better (the atomic mass of lithium is a notable, and serious, exception). This is adequate for almost all normal uses in chemistry: it is more precise than most chemical analyses, and exceeds the purity of most laboratory reagents. The precision of atomic masses, and hence of molar masses, is limited by the knowledge of the isotopic distribution of the element. If a more accurate value of the molar mass is required, it is necessary to determine the isotopic distribution of the sample in question, which may be different from the standard distribution used to calculate the standard atomic mass. The isotopic distributions of the different elements in a sample are not necessarily independent of one another: for example, a sample which has been distilled will be enriched in the lighter isotopes of all the elements present.


id: molecular-mass-20260505-0
file: data/en.wikipedia.org/wiki/Molecular_mass-0.md
category: reference
title: Molecular mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_mass
date_saved: 2026-05-05T10:53:02.533398+00:00
instance: kb-cron
parent: molecular-mass-20260505-0
summary:
The molecular mass (m) is the mass of a given molecule, often expressed in units of daltons (Da). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The derived quantity relative molecular mass is the unitless ratio of the mass of a molecule to the atomic mass constant (which is equal to one dalton). The molecular mass and relative molecular mass are distinct from but related to the molar mass. The molar mass is defined as the mass of a given substance divided by the amount of the substance, and is expressed in grams per mole (g/mol). That makes the molar mass an average of many particles or molecules (weighted by abundance of the isotopes), and the molecular mass the mass of one specific particle or molecule. The molar mass is usually the more appropriate quantity when dealing with macroscopic (weigh-able) quantities of a substance. The definition of molecular weight is most authoritatively synonymous with relative molecular mass, which is dimensionless; however, in common practice, use of this terminology is highly variable. When the molecular weight is given with the unit Da, it is frequently as a weighted average (by


id: molecular-mass-20260505-1
file: data/en.wikipedia.org/wiki/Molecular_mass-1.md
category: reference
title: Molecular mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Molecular_mass
date_saved: 2026-05-05T10:53:02.533398+00:00
instance: kb-cron
parent: molecular-mass-20260505-0
summary:
=== Hydrodynamic methods === To a first approximation, the basis for determination of molecular mass according to Mark–Houwink relations is the fact that the intrinsic viscosity of solutions (or suspensions) of macromolecules depends on volumetric proportion of the dispersed particles in a particular solvent. Specifically, the hydrodynamic size as related to molecular mass depends on a conversion factor, describing the shape of a particular molecule. This allows the apparent molecular mass to be described from a range of techniques sensitive to hydrodynamic effects, including DLS, SEC (also known as GPC when the eluent is an organic solvent), viscometry, and diffusion ordered nuclear magnetic resonance spectroscopy (DOSY). The apparent hydrodynamic size can then be used to approximate molecular mass using a series of macromolecule-specific standards. As this requires calibration, it's frequently described as a "relative" molecular mass determination method. === Static light scattering === It is also possible to determine absolute molecular mass directly from light scattering, traditionally using the Zimm method. This can be accomplished either via classical static light scattering or via multi-angle light scattering detectors. Molecular masses determined by this method do not require calibration, hence the term "absolute". The only external measurement required is refractive index increment,


id: monoisotopic-mass-20260505-0
file: data/en.wikipedia.org/wiki/Monoisotopic_mass-0.md
category: reference
title: Monoisotopic mass
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Monoisotopic_mass
date_saved: 2026-05-05T10:53:03.735277+00:00
instance: kb-cron
parent: monoisotopic-mass-20260505-0
summary:
Monoisotopic mass (Mmi) is one of several types of molecular masses used in mass spectrometry. The theoretical monoisotopic mass of a molecule is computed by taking the sum of the accurate masses (including mass defect) of the most abundant naturally occurring stable isotope of each atom in the molecule. It is also called the exact (a.k.a. theoretically determined) mass. For small molecules made up of low atomic number elements the monoisotopic mass is observable as an isotopically pure peak in a mass spectrum. This differs from the nominal molecular mass, which is the sum of the mass number of the primary isotope of each atom in the molecule and is an integer. It also is different from the molar mass, which is a type of average mass. For some atoms like carbon, oxygen, hydrogen, nitrogen, and sulfur, the Mmi of these elements is exactly the same as the mass of its natural isotope, which is the lightest one. However, this does not hold true for all atoms. Iron's most common isotope has a mass number of 56, while the stable isotopes of iron vary in mass number from 54 to 58. Monoisotopic mass is typically expressed in daltons (Da), also


id: natural-abundance-20260505-0
file: data/en.wikipedia.org/wiki/Natural_abundance-0.md
category: reference
title: Natural abundance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Natural_abundance
date_saved: 2026-05-05T10:53:04.946468+00:00
instance: kb-cron
parent: natural-abundance-20260505-0
summary:
In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass (a weighted average, weighted by mole-fraction abundance figures) of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from planet to planet, and even from place to place on the Earth, but remains relatively constant in time (on a short-term scale). As an example, uranium has three naturally occurring isotopes: 238U, 235U, and 234U. Their respective natural mole-fraction abundances are 99.2739–99.2752%, 0.7198–0.7202%, and 0.0050–0.0059%. For example, if 100,000 uranium atoms were analyzed, one would expect to find approximately 99,274 238U atoms, approximately 720 235U atoms, and very few (most likely 5 or 6) 234U atoms. This is because 238U is much more stable than 235U or 234U, as the half-life of each isotope reveals: 4.468 billion years for 238U compared with 7.038 × 108 years for 235U and 245,500 years for 234U. Exactly because the different uranium isotopes have different half-lives, when the Earth was younger, the isotopic composition of uranium was different. As an example, 1.7 billion years ago the NA of 235U


id: orders-of-magnitude-molar-concentration-20260505-0
file: data/en.wikipedia.org/wiki/Orders_of_magnitude_(molar_concentration)-0.md
category: reference
title: Orders of magnitude (molar concentration)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Orders_of_magnitude_(molar_concentration)
date_saved: 2026-05-05T10:53:06.133921+00:00
instance: kb-cron
parent: orders-of-magnitude-molar-concentration-20260505-0
summary:
This page lists examples of the orders of magnitude of molar concentration. Source values are parenthesized where unit conversions were performed. M denotes the non-SI unit molar: 1 M = 1 mol/L = 103 mol/m3. == All orders == == SI multiples == == See also == Molarity Osmolarity Metric system Scientific notation == References ==


id: oxidation-state-20260505-0
file: data/en.wikipedia.org/wiki/Oxidation_state-0.md
category: reference
title: Oxidation state
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oxidation_state
date_saved: 2026-05-05T10:53:07.516881+00:00
instance: kb-cron
parent: oxidation-state-20260505-0
summary:
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to other atoms are fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. Conceptually, the oxidation state may be positive, negative or zero. Beside nearly-pure ionic bonding, many covalent bonds exhibit a strong ionicity, making oxidation state a useful predictor of charge. The oxidation state of an atom does not represent the "real" charge on that atom, or any other actual atomic property. This is particularly true of high oxidation states, where the ionization energy required to produce a multiply positive ion is far greater than the energies available in chemical reactions. Additionally, the oxidation states of atoms in a given compound may vary depending on the choice of electronegativity scale used in their calculation. Thus, the oxidation state of an atom in a compound is purely a formalism. It is nevertheless important in understanding the nomenclature conventions of inorganic compounds. Also, several observations regarding chemical reactions may be explained at a basic level in terms of oxidation states. Oxidation states are typically represented by integers which may be positive, zero,


id: oxidation-state-20260505-1
file: data/en.wikipedia.org/wiki/Oxidation_state-1.md
category: reference
title: Oxidation state
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oxidation_state
date_saved: 2026-05-05T10:53:07.516881+00:00
instance: kb-cron
parent: oxidation-state-20260505-0
summary:
OS = +1 for hydrogen OS = −2 for oxygen where OS stands for oxidation state. This approach yields correct oxidation states in oxides and hydroxides of any single element, and in acids such as sulfuric acid (H2SO4) or dichromic acid (H2Cr2O7). Its coverage can be extended either by a list of exceptions or by assigning priority to the postulates. The latter works for hydrogen peroxide (H2O2) where the priority of rule 1 leaves both oxygens with oxidation state −1. Additional postulates and their ranking may expand the range of compounds to fit a textbook's scope. As an example, one postulatory algorithm from many possible; in a sequence of decreasing priority: An element in a free form has OS = 0. In a compound or ion, the sum of the oxidation states equals the total charge of the compound or ion. Fluorine in compounds has OS = −1; this extends to chlorine and bromine only when not bonded to a lighter halogen, oxygen or nitrogen. Group 1 and group 2 metals in compounds have OS = +1 and +2, respectively. Hydrogen has OS = +1 but adopts −1 when bonded as a hydride to metals or metalloids. Oxygen in compounds


id: oxidation-state-20260505-2
file: data/en.wikipedia.org/wiki/Oxidation_state-2.md
category: reference
title: Oxidation state
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oxidation_state
date_saved: 2026-05-05T10:53:07.516881+00:00
instance: kb-cron
parent: oxidation-state-20260505-0
summary:
Oxidation state is obtained by summing the heteronuclear-bond orders at the atom as positive if that atom is the electropositive partner in a particular bond and as negative if not, and the atom’s formal charge (if any) is added to that sum. The same caveat as above applies. ==== Applied to a Lewis structure ==== An example of a Lewis structure with no formal charge, illustrates that, in this algorithm, homonuclear bonds are simply ignored (the bond orders are in blue). Carbon monoxide exemplifies a Lewis structure with formal charges: To obtain the oxidation states, the formal charges are summed with the bond-order value taken positively at the carbon and negatively at the oxygen. Applied to molecular ions, this algorithm considers the actual location of the formal (ionic) charge, as drawn in the Lewis structure. As an example, summing bond orders in the ammonium cation yields −4 at the nitrogen of formal charge +1, with the two numbers adding to the oxidation state of −3: The sum of oxidation states in the ion equals its charge (as it equals zero for a neutral molecule). Also in anions, the formal (ionic) charges have to be considered when nonzero. For sulfate this


id: oxidation-state-20260505-3
file: data/en.wikipedia.org/wiki/Oxidation_state-3.md
category: reference
title: Oxidation state
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oxidation_state
date_saved: 2026-05-05T10:53:07.516881+00:00
instance: kb-cron
parent: oxidation-state-20260505-0
summary:
==== Oxidation-state determination from resonance formulas ==== Seemingly ambiguous oxidation states are derived from a set of resonance formulas of equal weights for a molecule having heteronuclear bonds where the atom connectivity does not correspond to the number of two-electron bonds dictated by the 8 − N rule. An example is S2N2 where four resonance formulas featuring one S=N double bond have oxidation states +2 and +4 for the two sulfur atoms, which average to +3 because the two sulfur atoms are equivalent in this square-shaped molecule. ==== A physical measurement is needed to determine oxidation state ==== when a non-innocent ligand is present, of hidden or unexpected redox properties that could otherwise be assigned to the central atom. An example is the nickel dithiolate complex, Ni(S2C2H2)2−2. when the redox ambiguity of a central atom and ligand yields dichotomous oxidation states of close stability, thermally induced tautomerism may result, as exemplified by manganese catecholate, Mn(C6H4O2)3. Assignment of such oxidation states requires spectroscopic, magnetic or structural data. when the bond order has to be ascertained along with an isolated tandem of a heteronuclear and a homonuclear bond. An example is thiosulfate S2O2−3 having two possible oxidation states (bond orders are in


id: oxidation-state-20260505-4
file: data/en.wikipedia.org/wiki/Oxidation_state-4.md
category: reference
title: Oxidation state
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oxidation_state
date_saved: 2026-05-05T10:53:07.516881+00:00
instance: kb-cron
parent: oxidation-state-20260505-0
summary:
== List of oxidation states of the elements == This is a list of known oxidation states of the chemical elements, excluding nonintegral values. The most common states appear in bold. The table is based on that of Greenwood and Earnshaw, with additions noted. Every element exists in oxidation state 0 when it is the pure non-ionized element in any phase, whether monatomic or polyatomic allotrope. The column for oxidation state 0 only shows elements known to exist in oxidation state 0 in compounds. === Early forms (octet rule) === A figure with a similar format was used by Irving Langmuir in 1919 in one of the early papers about the octet rule. The periodicity of the oxidation states was one of the pieces of evidence that led Langmuir to adopt the rule. == Use in nomenclature == The oxidation state in compound naming for transition metals and lanthanides and actinides is placed either as a right superscript to the element symbol in a chemical formula, such as FeIII or in parentheses after the name of the element in chemical names, such as iron(III). For example, Fe2(SO4)3 is named iron(III) sulfate and its formula can be shown as FeIII2(SO4)3. This


id: oxidizing-agent-20260505-0
file: data/en.wikipedia.org/wiki/Oxidizing_agent-0.md
category: reference
title: Oxidizing agent
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Oxidizing_agent
date_saved: 2026-05-05T10:53:08.746096+00:00
instance: kb-cron
parent: oxidizing-agent-20260505-0
summary:
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "accepts"/"receives" an electron from a reducing agent (called the reductant, reducer, or electron donor). In other words, an oxidizer is any substance that oxidizes another substance. The oxidation state, which describes the degree of loss of electrons, of the oxidizer decreases while that of the reductant increases; this is expressed by saying that oxidizers "undergo reduction" and "are reduced" while reducers "undergo oxidation" and "are oxidized". Common oxidizing agents are oxygen, hydrogen peroxide, and the halogens. In one sense, an oxidizing agent is a chemical species that undergoes a chemical reaction in which it gains one or more electrons. In that sense, it is one component in an oxidation–reduction (redox) reaction. In the second sense, an oxidizing agent is a chemical species that transfers electronegative atoms, usually oxygen, to a substrate. Combustion, many explosives, and organic redox reactions involve atom-transfer reactions. == Electron acceptors == Electron acceptors participate in electron-transfer reactions. In this context, the oxidizing agent is called an electron acceptor and the reducing agent is called an electron donor. A classic oxidizing agent


id: polyvalency-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Polyvalency_(chemistry)-0.md
category: reference
title: Polyvalency (chemistry)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Polyvalency_(chemistry)
date_saved: 2026-05-05T10:53:09.897306+00:00
instance: kb-cron
parent: polyvalency-chemistry-20260505-0
summary:
In chemistry, polyvalency (or polyvalence, multivalency) is the property of molecules and larger species, such as antibodies, medical drugs, and even nanoparticles surface-functionalized with ligands, like spherical nucleic acids, that exhibit more than one supramolecular interaction. For the number of chemical bonds of atoms, the term "valence" is used (Fig. 1). For both atoms and larger species, the number of bonds may be specified: divalent species can form two bonds; a trivalent species can form three bonds; and so on. Species that have polyvalency usually show enhanced or cooperative binding compared to their monovalent counterparts. Nanoparticles with multiple nucleic acid strands on their surfaces (e.g., DNA) can form multiple bonds with one another by DNA hybridization to form hierarchical assemblies, some of which are highly crystalline in nature. == References ==


id: pour-point-20260505-0
file: data/en.wikipedia.org/wiki/Pour_point-0.md
category: reference
title: Pour point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pour_point
date_saved: 2026-05-05T10:53:11.098669+00:00
instance: kb-cron
parent: pour-point-20260505-0
summary:
The pour point of a liquid is the temperature below which the liquid loses its flow characteristics. It is defined as the minimum temperature in which the oil has the ability to pour down from a beaker. In crude oil a high pour point is generally associated with a high paraffin content, typically found in crude deriving from a larger proportion of plant material. That type of crude oil is mainly derived from a kerogen Type III. == Measuring the pour point of petroleum products == === Manual method === ASTM D97, Standard Test Method for Pour Point of Crude Oils. The specimen is cooled inside a cooling bath to allow the formation of paraffin wax crystals. At about 9 °C (16 °F) above the expected pour point, and for every subsequent 3 °C (5.4 °F), the test jar is removed and tilted to check for surface movement. When the specimen does not flow when tilted, the jar is held horizontally for 5 seconds. If it does not flow, 3 °C is added to the corresponding temperature and the result is the pour point temperature. It is also useful to note that failure to flow at the pour point may


id: proton-affinity-20260505-0
file: data/en.wikipedia.org/wiki/Proton_affinity-0.md
category: reference
title: Proton affinity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Proton_affinity
date_saved: 2026-05-05T10:53:12.305426+00:00
instance: kb-cron
parent: proton-affinity-20260505-0
summary:
The proton affinity (PA, Epa) of an anion or of a neutral atom or molecule is the negative of the enthalpy change in the reaction between the chemical species concerned and a proton in the gas phase: A − + H + ⟶ HA {\displaystyle {\ce {A- + H+ -> HA}}} B + H + ⟶ BH + {\displaystyle {\ce {B + H+ -> BH+}}} These reactions are always exothermic in the gas phase, i.e. energy is released (enthalpy is negative) when the reaction advances in the direction shown above, while the proton affinity is positive. This is the same sign convention used for electron affinity. The property related to the proton affinity is the gas-phase basicity, which is the negative of the Gibbs energy for above reactions, i.e. the gas-phase basicity includes entropic terms in contrast to the proton affinity. == Acid/base chemistry == The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase. The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (Epa = 1843 kJ/mol), followed by the methanide anion (Epa = 1743 kJ/mol) and the hydride ion (Epa = 1675 kJ/mol), making methane the weakest proton acid


id: psychrometric-constant-20260505-0
file: data/en.wikipedia.org/wiki/Psychrometric_constant-0.md
category: reference
title: Psychrometric constant
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Psychrometric_constant
date_saved: 2026-05-05T10:53:13.705446+00:00
instance: kb-cron
parent: psychrometric-constant-20260505-0
summary:
The psychrometric constant γ {\displaystyle \gamma } relates the partial pressure of water in air to the air temperature. This lets one interpolate actual vapor pressure from paired dry and wet thermometer bulb temperature readings. γ = ( c p ) a i r ∗ P λ v ∗ M W r a t i o {\displaystyle \gamma ={\frac {\left(c_{p}\right)_{air}*P}{\lambda _{v}*MW_{ratio}}}} γ = {\displaystyle \gamma =} psychrometric constant [kPa °C−1], P = atmospheric pressure [kPa], λ v = {\displaystyle \lambda _{v}=} latent heat of water vaporization, 2.45 [MJ kg−1], c p = {\displaystyle c_{p}=} specific heat of air at constant pressure, [MJ kg−1 °C−1], M W r a t i o = {\displaystyle MW_{ratio}=} ratio molecular weight of water vapor/dry air = 0.622. Both λ v {\displaystyle \lambda _{v}} and M W r a t i o {\displaystyle MW_{ratio}} are constants. Since atmospheric pressure, P, depends upon altitude, so does γ {\displaystyle \gamma } . At higher altitude water evaporates and boils at lower temperature. Although ( c p ) H 2 O {\displaystyle \left(c_{p}\right)_{H_{2}O}} is constant, varied air composition results in varied ( c p ) a i r {\displaystyle \left(c_{p}\right)_{air}} . Thus on average, at a given location


id: pyrophoricity-20260505-0
file: data/en.wikipedia.org/wiki/Pyrophoricity-0.md
category: reference
title: Pyrophoricity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Pyrophoricity
date_saved: 2026-05-05T10:53:14.875891+00:00
instance: kb-cron
parent: pyrophoricity-20260505-0
summary:
A substance is pyrophoric (from Ancient Greek: πυροφόρος, pyrophoros, 'fire-bearing') if it ignites spontaneously in air at or below 54 °C (129 °F) (for gases) or within five minutes after coming into contact with air (for liquids and solids). Examples are organolithium compounds and triethylborane, as well as actinides. Pyrophoric materials are often water-reactive as well and will ignite when they contact water or humid air. They can be handled safely in atmospheres of argon or (with a few exceptions) nitrogen. Class D fire extinguishers are designated for use in fires involving metals but not pyrophoric materials in general. A related concept is hypergolicity, in which two compounds spontaneously ignite when mixed. == Uses == The creation of sparks from metals is based on the pyrophoricity of small metal particles, and pyrophoric alloys are made for this purpose. Practical applications include the sparking mechanisms in lighters and various toys, using ferrocerium; starting fires without matches, using a firesteel; the flintlock mechanism in firearms; and spark testing ferrous metals. == Handling == The type of equipment required for transporting, handling and working with pyrophoric materials depends on the amounts of the materials and their flammability risks. Small amounts of pyrophoric liquids


id: reactivity-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Reactivity_(chemistry)-0.md
category: reference
title: Reactivity (chemistry)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reactivity_(chemistry)
date_saved: 2026-05-05T10:53:16.085439+00:00
instance: kb-cron
parent: reactivity-chemistry-20260505-0
summary:
In chemistry, reactivity is the impulse for which a chemical substance undergoes a chemical reaction, either by itself or with other materials, with an overall release of energy. Reactivity refers to: the chemical reactions of a single substance, the chemical reactions of two or more substances that interact with each other, the systematic study of sets of reactions of these two kinds, methodology that applies to the study of reactivity of chemicals of all kinds, experimental methods that are used to observe these processes, and theories to predict and to account for these processes. The chemical reactivity of a single substance (reactant) covers its behavior in which it: decomposes, forms new substances by addition of atoms from another reactant or reactants, and interacts with two or more other reactants to form two or more products. The chemical reactivity of a substance can refer to the variety of circumstances (conditions that include temperature, pressure, presence of catalysts) in which it reacts, in combination with the: variety of substances with which it reacts, equilibrium point of the reaction (i.e., the extent to which all of it reacts), and rate of the reaction. The term reactivity is related to the concepts of chemical


id: refractory-20260505-0
file: data/en.wikipedia.org/wiki/Refractory-0.md
category: reference
title: Refractory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refractory
date_saved: 2026-05-05T10:53:17.244522+00:00
instance: kb-cron
parent: refractory-20260505-0
summary:
In materials science, a refractory (or refractory material) is a material that is resistant to decomposition by heat or chemical attack and that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compounds that may be porous or non-porous, and their crystallinity varies widely: they may be crystalline, polycrystalline, amorphous, or composite. They are typically composed of oxides, carbides or nitrides of the following elements: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium. Many refractories are ceramics, but some such as graphite are not, and some ceramics such as clay pottery are not considered refractory. Refractories are distinguished from the refractory metals, which are elemental metals and their alloys that have high melting temperatures. Refractories are defined by ASTM C71 as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 1,000 °F (811 K; 538 °C)". Refractory materials are used in furnaces, kilns, incinerators, and reactors. Refractories are also used to make crucibles and molds for casting glass and metals. The iron and steel industry and metal casting sectors use approximately 70% of all refractories produced. == Refractory materials == Refractory


id: refractory-20260505-1
file: data/en.wikipedia.org/wiki/Refractory-1.md
category: reference
title: Refractory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Refractory
date_saved: 2026-05-05T10:53:17.244522+00:00
instance: kb-cron
parent: refractory-20260505-0
summary:
==== Neutral refractories ==== These are used in areas where slags and atmosphere are either acidic or basic and are chemically stable to both acids and bases. The main raw materials belong to, but are not confined to, the R2O3 group. Common examples of these materials are alumina (Al2O3), chromia (Cr2O3) and carbon. Carbon graphite refractories mainly consist of carbon. These refractories are often used in highly reducing environments, and their properties of high refractoriness allow them excellent thermal stability and resistance to slags. Chromite refractories are composed of sintered magnesia and chromia. They have constant volume at high temperatures, high refractoriness, and high resistance to slags. Alumina refractories are composed of ≥ 50% alumina (Al2O3). === Method of manufacture === Dry press process Fused cast Hand molded Formed (normal, fired or chemically bonded) Un-formed (monolithic-plastic, ramming and gunning mass, castables, mortars, dry vibrating cements.) Un-formed dry refractories. === Size and shape === Refractory objects are manufactured in standard shapes and special shapes. Standard shapes have dimensions that conform to conventions used by refractory manufacturers and are generally applicable to kilns or furnaces of the same types. Standard shapes are usually bricks that have a standard dimension of 9 in


id: reid-vapor-pressure-20260505-0
file: data/en.wikipedia.org/wiki/Reid_vapor_pressure-0.md
category: reference
title: Reid vapor pressure
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reid_vapor_pressure
date_saved: 2026-05-05T10:53:18.396897+00:00
instance: kb-cron
parent: reid-vapor-pressure-20260505-0
summary:
Reid vapor pressure (RVP) is a common measure of the volatility of gasoline and other petroleum products. It is defined as the vapor pressure exerted by the vapor of the liquid and any dissolved gases/moisture at 37.8 °C (100 °F) as determined by the test method ASTM-D-323, which was first developed in 1930 and has been revised several times (the latest version is ASTM D323-15a). The test method measures the vapor pressure of gasoline, volatile crude oil, aviation gasoline, naphtha, and other volatile petroleum products but is not applicable for liquefied petroleum gases. ASTM D323-15a requires that the sample be chilled to 0 to 1 degrees Celsius, air-saturated at this temperature and then poured into the apparatus; for any material that solidifies at this temperature, this step cannot be performed. RVP is commonly reported in kilopascals (kPa) or pounds per square inch (psi) and represents volatization at atmospheric pressure because ASTM-D-323 measures the gauge pressure of the sample in a non-evacuated chamber. The matter of vapor pressure is important relating to the function and operation of gasoline-powered, especially carbureted, vehicles and is also important for many other reasons. High levels of vaporization are desirable for winter starting and operation and


id: rot-proof-20260505-0
file: data/en.wikipedia.org/wiki/Rot-proof-0.md
category: reference
title: Rot-proof
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rot-proof
date_saved: 2026-05-05T10:53:19.567660+00:00
instance: kb-cron
parent: rot-proof-20260505-0
summary:
Rot-proof or rot resistant is a condition of preservation or protection, by a process or treatment of materials used in industrial manufacturing or production to prevent biodegradation and chemical decomposition. Decomposition is a factor in which organic matter breaks down over time. It is commonly caused by fungus, mold or mildew. There are natural conditions where the environment is inhospitable to animals, bacteria and fungus, for example in high altitude and the freezing subzero temperatures of the Arctic and Antarctic, which creates a similar suspension. The proofing of materials may also prevent dry rot and wet rot. == See also == Dust resistant Fireproofing Rustproofing Thermal resistant Toughness Waterproofing


id: smoke-point-20260505-0
file: data/en.wikipedia.org/wiki/Smoke_point-0.md
category: reference
title: Smoke point
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Smoke_point
date_saved: 2026-05-05T10:53:20.743224+00:00
instance: kb-cron
parent: smoke-point-20260505-0
summary:
The smoke point, also referred to as the burning point, is the temperature at which an oil or fat begins to produce a continuous bluish smoke that becomes clearly visible, dependent upon specific and defined conditions. This happens when one or multiple substances in the oil start to chemically react with oxygen and burn, which can include the oil itself, proteins, sugars, or other organic material. It is distinct from the flash point and fire point, which denote the temperatures at which the oil itself (specifically, vaporized oil, which is distinct from the smoke produced at the smoke point) begins to burn. Smoke point values can vary greatly. The most important factor determining the smoke point of an oil is the amount of proteins and free fatty acids (FFAs). Higher quantities of these lower the smoke point. The FFA content typically represents less than 1% of the total oil and consequently renders smoke point a poor indicator of the capacity of a fat or oil to withstand heat, in a non-cuisine related sense. Virgin (raw) oils, which contain various flavorful organic compounds, have lower smoke points than refined oils because the organic compounds burn. Animal-based fats and oils tend to


id: solubility-20260505-0
file: data/en.wikipedia.org/wiki/Solubility-0.md
category: reference
title: Solubility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solubility
date_saved: 2026-05-05T10:53:21.932559+00:00
instance: kb-cron
parent: solubility-20260505-0
summary:
In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubility of a substance in a specific solvent is generally measured as the concentration of the solute in a saturated solution, one in which no more solute can be dissolved. At this point, the two substances are said to be at the solubility equilibrium. For some solutes and solvents, there may be no such limit, in which case the two substances are said to be "miscible in all proportions" (or just "miscible"). The solute can be a solid, a liquid, or a gas, while the solvent is usually solid or liquid. Both may be pure substances, or may themselves be solutions. Gases are always miscible in all proportions, except in very extreme situations, and a solid or liquid can be "dissolved" in a gas only by passing into the gaseous state first. The solubility mainly depends on the composition of solute and solvent (including their pH and the presence of other dissolved substances) as well as on temperature and pressure. The


id: solubility-20260505-1
file: data/en.wikipedia.org/wiki/Solubility-1.md
category: reference
title: Solubility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solubility
date_saved: 2026-05-05T10:53:21.932559+00:00
instance: kb-cron
parent: solubility-20260505-0
summary:
=== Conversion of solubility values === Conversion between these various ways of measuring solubility may not be trivial, since it may require knowing the density of the solution—which is often not measured, and cannot be predicted. While the total mass is conserved by dissolution, the final volume may be different from both the volume of the solvent and the sum of the two volumes. Moreover, many solids (such as acids and salts) will dissociate in non-trivial ways when dissolved; conversely, the solvent may form coordination complexes with the molecules or ions of the solute. In those cases, the sum of the moles of molecules of solute and solvent is not really the total moles of independent particles solution. To sidestep that problem, the solubility per mole of solution is usually computed and quoted as if the solute does not dissociate or form complexes—that is, by pretending that the mole amount of solution is the sum of the mole amounts of the two substances. == Qualifiers used to describe extent of solubility == The extent of solubility ranges widely, from infinitely soluble (without limit, i.e. miscible) such as ethanol in water, to essentially insoluble, such as titanium dioxide in water. A


id: solubility-20260505-2
file: data/en.wikipedia.org/wiki/Solubility-2.md
category: reference
title: Solubility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solubility
date_saved: 2026-05-05T10:53:21.932559+00:00
instance: kb-cron
parent: solubility-20260505-0
summary:
For most solids and liquids, their solubility increases with temperature because their dissolution reaction is endothermic (ΔH > 0). In liquid water at high temperatures, (e.g. that approaching the critical temperature), the solubility of ionic solutes tends to decrease due to the change of properties and structure of liquid water; the lower dielectric constant results in a less polar solvent and in a change of hydration energy affecting the ΔG of the dissolution reaction. Gaseous solutes exhibit more complex behavior with temperature. As the temperature is raised, gases usually become less soluble in water (exothermic dissolution reaction related to their hydration) (to a minimum, which is below 120 °C for most permanent gases), but more soluble in organic solvents (endothermic dissolution reaction related to their solvation). The chart shows solubility curves for some typical solid inorganic salts in liquid water (temperature is in degrees Celsius, i.e. kelvins minus 273.15). Many salts behave like barium nitrate and disodium hydrogen arsenate, and show a large increase in solubility with temperature (ΔH > 0). Some solutes (e.g. sodium chloride in water) exhibit solubility that is fairly independent of temperature (ΔH ≈ 0). A few, such as calcium sulfate (gypsum) and cerium(III) sulfate, become


id: solubility-20260505-3
file: data/en.wikipedia.org/wiki/Solubility-3.md
category: reference
title: Solubility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solubility
date_saved: 2026-05-05T10:53:21.932559+00:00
instance: kb-cron
parent: solubility-20260505-0
summary:
== Polarity == A popular aphorism used for predicting solubility is "like dissolves like" also expressed in the Latin language as "Similia similibus solventur". This statement indicates that a solute will dissolve best in a solvent that has a similar chemical structure to itself, based on favorable entropy of mixing. This view is simplistic, but it is a useful rule of thumb. The overall solvation capacity of a solvent depends primarily on its polarity. For example, a very polar (hydrophilic) solute such as urea is very soluble in highly polar water, less soluble in fairly polar methanol, and practically insoluble in non-polar solvents such as benzene. In contrast, a non-polar or lipophilic solute such as naphthalene is insoluble in water, fairly soluble in methanol, and highly soluble in non-polar benzene. In even more simple terms a simple ionic compound (with positive and negative ions) such as sodium chloride (common salt) is easily soluble in a highly polar solvent (with some separation of positive (δ+) and negative (δ-) charges in the covalent molecule) such as water, as thus the sea is salty as it accumulates dissolved salts since early geological ages. The solubility is favored by entropy of mixing (ΔS) and


id: solubility-20260505-4
file: data/en.wikipedia.org/wiki/Solubility-4.md
category: reference
title: Solubility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solubility
date_saved: 2026-05-05T10:53:21.932559+00:00
instance: kb-cron
parent: solubility-20260505-0
summary:
== Applications == Solubility is of fundamental importance in a large number of scientific disciplines and practical applications, ranging from ore processing and nuclear reprocessing to the use of medicines, and the transport of pollutants. Solubility is often said to be one of the "characteristic properties of a substance", which means that solubility is commonly used to describe the substance, to indicate a substance's polarity, to help to distinguish it from other substances, and as a guide to applications of the substance. For example, indigo is described as "insoluble in water, alcohol, or ether but soluble in chloroform, nitrobenzene, or concentrated sulfuric acid". Solubility of a substance is useful when separating mixtures. For example, a mixture of salt (sodium chloride) and silica may be separated by dissolving the salt in water, and filtering off the undissolved silica. The synthesis of chemical compounds, by the milligram in a laboratory, or by the ton in industry, both make use of the relative solubilities of the desired product, as well as unreacted starting materials, byproducts, and side products to achieve separation. Another example of this is the synthesis of benzoic acid from phenylmagnesium bromide and dry ice. Benzoic acid is more soluble in


id: solubility-20260505-5
file: data/en.wikipedia.org/wiki/Solubility-5.md
category: reference
title: Solubility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solubility
date_saved: 2026-05-05T10:53:21.932559+00:00
instance: kb-cron
parent: solubility-20260505-0
summary:
== Solid solution == This term is often used in the field of metallurgy to refer to the extent that an alloying element will dissolve into the base metal without forming a separate phase. The solvus or solubility line (or curve) is the line (or lines) on a phase diagram that give the limits of solute addition. That is, the lines show the maximum amount of a component that can be added to another component and still be in solid solution. In the solid's crystalline structure, the 'solute' element can either take the place of the matrix within the lattice (a substitutional position; for example, chromium in iron) or take a place in a space between the lattice points (an interstitial position; for example, carbon in iron). In microelectronic fabrication, solid solubility refers to the maximum concentration of impurities one can place into the substrate. In solid compounds (as opposed to elements), the solubility of a solute element can also depend on the phases separating out in equilibrium. For example, amount of Sn soluble in the ZnSb phase can depend significantly on whether the phases separating out in equilibrium are (Zn4Sb3+Sn(L)) or (ZnSnSb2+Sn(L)). Besides these, the ZnSb compound with Sn


id: solubility-20260505-6
file: data/en.wikipedia.org/wiki/Solubility-6.md
category: reference
title: Solubility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solubility
date_saved: 2026-05-05T10:53:21.932559+00:00
instance: kb-cron
parent: solubility-20260505-0
summary:
log 10 ⁡ ( S ) = 0.5 − log 10 ⁡ ( P ) − 0.01 ( melting point − 25 ) {\displaystyle \log _{10}(S)=0.5-\log _{10}(P)-0.01({\text{melting point}}-25)} These equations are founded on the principles of the fusion cycle. == See also == Apparent molar property – Difference in properties of one mole of substance in a mixture vs. an ideal solution Biopharmaceutics Classification System – System to differentiate drugs on the basis of their solubility and permeability Dühring's rule – Rule in thermodynamics Fajans–Paneth–Hahn Law – Chemistry rule concerning co-precipitation and adsorption Flexible SPC water model – Aspect of computational chemistryPages displaying short descriptions of redirect targets Henry's law – Gas law regarding proportionality of dissolved gas Hot water extraction – Method of carpet cleaning Hydrotrope – Chemical substance Micellar solubilization – Process of incorporating the solubilizate into or onto micelles Raoult's law – Law of thermodynamics for vapour pressure of a mixture Rate of solution – Capacity of a substance to dissolve in a homogeneous wayPages displaying short descriptions of redirect targets Solubility equilibrium – Thermodynamic equilibrium between a solid and a solution of the same compound Van 't Hoff equation – Relation between temperature and the equilibrium


id: solvation-shell-20260505-0
file: data/en.wikipedia.org/wiki/Solvation_shell-0.md
category: reference
title: Solvation shell
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solvation_shell
date_saved: 2026-05-05T10:53:23.113007+00:00
instance: kb-cron
parent: solvation-shell-20260505-0
summary:
A solvation shell or solvation sheath is the solvent interface of any chemical compound or biomolecule that constitutes the solute in a solution. When the solvent is water it is called a hydration shell or hydration sphere. The number of solvent molecules surrounding each unit of solute is called the hydration number of the solute. A classic example is when water molecules arrange around a metal ion. If the metal ion is a cation, the electronegative oxygen atom of the water molecule would be attracted electrostatically to the positive charge on the metal ion. The result is a solvation shell of water molecules that surround the ion. This shell can be several molecules thick, dependent upon the charge of the ion, its distribution and spatial dimensions. A number of molecules of solvent are involved in the solvation shell around anions and cations from a dissolved salt in a solvent. Metal ions in aqueous solutions form metal aquo complexes. This number can be determined by various methods like compressibility and NMR measurements among others. == Relation to activity coefficient of an electrolyte and its solvation shell number == The solvation shell number of a dissolved electrolyte can be linked to the


id: specific-rotation-20260505-0
file: data/en.wikipedia.org/wiki/Specific_rotation-0.md
category: reference
title: Specific rotation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Specific_rotation
date_saved: 2026-05-05T10:53:24.353865+00:00
instance: kb-cron
parent: specific-rotation-20260505-0
summary:
In chemistry, specific rotation ([α]) is a property of a chiral chemical compound. It is defined as the change in orientation of monochromatic plane-polarized light, per unit distance–concentration product, as the light passes through a sample of a compound in solution. Compounds which rotate the plane of polarization of a beam of plane polarized light clockwise are said to be dextrorotary, and correspond with positive specific rotation values, while compounds which rotate the plane of polarization of plane polarized light counterclockwise are said to be levorotary, and correspond with negative values. If a compound is able to rotate the plane of polarization of plane-polarized light, it is said to be “optically active”. Specific rotation is an intensive property, distinguishing it from the more general phenomenon of optical rotation. As such, the observed rotation (α) of a sample of a compound can be used to quantify the enantiomeric excess of that compound, provided that the specific rotation ([α]) for the enantiopure compound is known. The variance of specific rotation with wavelength—a phenomenon known as optical rotatory dispersion—can be used to find the absolute configuration of a molecule. The concentration of bulk sugar solutions is sometimes determined by comparison of the observed


id: speed-of-sound-20260505-0
file: data/en.wikipedia.org/wiki/Speed_of_sound-0.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn), or 1 km in 2.92 s or one mile in 4.69 s. It depends strongly on temperature as well as the medium through which a sound wave is propagating. At 0 °C (32 °F), the speed of sound in dry air (sea level 14.7 psi) is about 331 m/s (1,086 ft/s; 1,192 km/h; 740 mph; 643 kn). The speed of sound in an ideal gas depends only on its temperature and composition. The speed has a weak dependence on frequency and pressure in dry air, deviating slightly from ideal behavior. In colloquial speech, speed of sound refers to the speed of sound waves in air. The speed of sound varies from substance to substance, however: typically, sound travels most slowly in gases, faster in liquids, and fastest in solids. For example, while sound travels at 343 m/s in air, it travels in fresh


id: speed-of-sound-20260505-1
file: data/en.wikipedia.org/wiki/Speed_of_sound-1.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
== History == The Pythagorean Archytas taught that higher pitched sound travels faster, an opinion accepted by some subsequent philosophers, such as those of the Academy and the Peripatos, including possibly Aristotle. Sir Isaac Newton's 1687 Principia includes a computation of the speed of sound in air as 979 feet per second (298 m/s). This is too low by about 15%. The discrepancy is due primarily to neglecting the (then unknown) effect of rapidly fluctuating temperature in a sound wave (in modern terms, sound wave compression and expansion of air is an adiabatic process, not an isothermal process). Newton then invented various fudge factors, such as the "crassitude of the solid particles of the air", until the number agreed with the experimental measurement. Lagrange and Euler both attempted and failed to explain the discrepancy. This discrepancy was finally correctly explained by Pierre-Simon Laplace. In Traité de mécanique céleste, he used the result from the Clément-Desormes experiment of 1819, which measured the heat capacity ratio of air to be 1.35. This produced a near agreement between theory and experiment for the speed of sound. The modern value of 1.40 was found some years later, leading to complete agreement. During the 17th


id: speed-of-sound-20260505-2
file: data/en.wikipedia.org/wiki/Speed_of_sound-2.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
== Compression and shear waves == In a gas or liquid, sound consists of compression waves. In solids, waves propagate as two different types. A longitudinal wave is associated with compression and decompression in the direction of travel, and is the same process in gases and liquids, with an analogous compression-type wave in solids. Only compression waves are propagated through fluids (gases and liquids). An additional type of wave, the transverse wave, also called a shear wave, occurs only in solids because only solids support elastic deformations. It is due to elastic deformation of the medium perpendicular to the direction of wave travel; the direction of shear deformation is called the "polarization" of this type of wave. In general, transverse waves occur as a pair of orthogonal polarizations. These different waves (compression waves and the different polarizations of shear waves) may have different speeds at the same frequency. Therefore, they arrive at an observer at different times, an extreme example being an earthquake, where sharp compression waves arrive first and rocking transverse waves seconds later. The speed of a compression wave in a fluid is determined by the medium's compressibility and density. In solids, the compression waves are analogous to


id: speed-of-sound-20260505-3
file: data/en.wikipedia.org/wiki/Speed_of_sound-3.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
== Dependence on the properties of the medium == The speed of sound is variable and depends on the properties of the substance through which the wave is travelling. In solids, the speed of transverse (or shear) waves depends on the shear deformation under shear stress (called the shear modulus), and the density of the medium. Longitudinal (or compression) waves in solids depend on the same two factors with the addition of a dependence on compressibility. In fluids, only the medium's compressibility and density are the important factors, since fluids do not transmit shear stresses. In heterogeneous fluids, such as a liquid filled with gas bubbles, the density of the liquid and the compressibility of the gas affect the speed of sound in an additive manner, as demonstrated in the hot chocolate effect. In gases, adiabatic compressibility is directly related to pressure through the heat capacity ratio (adiabatic index), while pressure and density are inversely related to the temperature and molecular weight, thus making only the completely independent properties of temperature and molecular structure important (heat capacity ratio may be determined by temperature and molecular structure, but simple molecular weight is not sufficient to determine it). Sound propagates faster in


id: speed-of-sound-20260505-4
file: data/en.wikipedia.org/wiki/Speed_of_sound-4.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
c i d e a l = γ p ρ = γ R T M = γ k T m = 1.380649 ⋅ 10 − 23 ⋅ γ T m ≈ 8.314 γ T M { = 1.9329086 ⋅ 10 − 23 ⋅ T m ≈ 11.640 T M , γ = 7 5 ≈ 2.301 ⋅ 10 − 23 ⋅ T m ≈ 13.857 T M , γ = 5 3 ≈ 1.840 ⋅ 10 − 23 ⋅ T m ≈ 11.086 T M , γ = 4 3 c d r y a i r ≈ 20.04687087513010149970678963 T {\displaystyle {\begin{aligned}c_{\mathrm {ideal} }&={\sqrt {\frac {\gamma p}{\rho }}}={\sqrt {\frac {\gamma RT}{M}}}={\sqrt {\frac {\gamma kT}{m}}}\\&={\sqrt {\frac {1.380649\cdot 10^{-23}\cdot \gamma T}{m}}}\approx {\sqrt {\frac {8.314\gamma T}{M}}}\\&{\begin{cases}&={\sqrt {\frac {1.9329086\cdot 10^{-23}\cdot T}{m}}}\approx {\sqrt {\frac {11.640T}{M}}},&&\gamma ={\frac {7}{5}}\\&\approx {\sqrt {\frac {2.301\cdot 10^{-23}\cdot T}{m}}}\approx {\sqrt {\frac {13.857T}{M}}},&&\gamma ={\frac {5}{3}}\\&\approx {\sqrt {\frac {1.840\cdot 10^{-23}\cdot T}{m}}}\approx {\sqrt {\frac {11.086T}{M}}},&&\gamma ={\frac {4}{3}}\\\end{cases}}\\c_{\mathrm {dry\ air} }&\approx 20.04687087513010149970678963{\sqrt {T}}\end{aligned}}} where cideal is the speed of sound in an ideal gas; p is the pressure; ρ is the density; γ (gamma) is the adiabatic index. At room temperature, where thermal energy is fully partitioned into rotation (rotations are fully excited) but quantum effects


id: speed-of-sound-20260505-5
file: data/en.wikipedia.org/wiki/Speed_of_sound-5.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
=== Effects due to wind shear === The speed of sound varies with temperature. Since temperature and sound velocity normally decrease with increasing altitude, sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. Wind shear of 4 m/(s · km) can produce refraction equal to a typical temperature lapse rate of 7.5 °C/km. Higher values of wind gradient will refract sound downward toward the surface in the downwind direction, eliminating the acoustic shadow on the downwind side. This will increase the audibility of sounds downwind. This downwind refraction effect occurs because there is a wind gradient; the fact that sound is carried along by the wind is not important. For sound propagation, the exponential variation of wind speed with height can be defined as follows: U ( h ) = U ( 0 ) h ζ , d U d h ( h ) = ζ U ( h ) h , {\displaystyle {\begin{aligned}U(h)&=U(0)h^{\zeta },\\{\frac {\mathrm {d} U}{\mathrm {d} h}}(h)&=\zeta {\frac {U(h)}{h}},\end{aligned}}} where U(h) is the speed of the wind at height h; ζ is the exponential coefficient based on ground surface roughness, typically between 0.08 and 0.52; dU/dh(h)


id: speed-of-sound-20260505-6
file: data/en.wikipedia.org/wiki/Speed_of_sound-6.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
=== Practical application to air === By far, the most important factor influencing the speed of sound in air is temperature. The speed is proportional to the square root of the absolute temperature, giving an increase of about 0.6 m/s per degree Celsius. For this reason, the pitch of a musical wind instrument increases as its temperature increases. The speed of sound is raised by humidity. The difference between 0% and 100% humidity is about 1.5 m/s at standard pressure and temperature, but the size of the humidity effect increases dramatically with temperature. The dependence on frequency and pressure are normally insignificant in practical applications. In dry air, the speed of sound increases by about 0.1 m/s as the frequency rises from 10 Hz to 100 Hz. For audible frequencies above 100 Hz it is relatively constant. Standard values of the speed of sound are quoted in the limit of low frequencies, where the wavelength is large compared to the mean free path. As shown above, the approximate value 1000/3 = 333.33... m/s is exact a little below 5 °C and is a good approximation for all "usual" outside temperatures (in temperate climates, at least), hence the usual rule of


id: speed-of-sound-20260505-7
file: data/en.wikipedia.org/wiki/Speed_of_sound-7.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
==== Three-dimensional solids ==== In a solid, there is a non-zero stiffness both for volumetric deformations and shear deformations. Hence, it is possible to generate sound waves with different velocities dependent on the deformation mode. Sound waves generating volumetric deformations (compression) and shear deformations (shearing) are called pressure waves (longitudinal waves) and shear waves (transverse waves), respectively. In earthquakes, the corresponding seismic waves are called P-waves (primary waves) and S-waves (secondary waves), respectively. The sound velocities of these two types of waves propagating in a homogeneous 3-dimensional solid are respectively given by c solid,p = K + 4 3 G ρ = E ( 1 − ν ) ρ ( 1 + ν ) ( 1 − 2 ν ) , {\displaystyle c_{\text{solid,p}}={\sqrt {\frac {K+{\frac {4}{3}}G}{\rho }}}={\sqrt {\frac {E(1-\nu )}{\rho (1+\nu )(1-2\nu )}}},} c solid,s = G ρ , {\displaystyle c_{\text{solid,s}}={\sqrt {\frac {G}{\rho }}},} where K is the bulk modulus of the elastic materials; G is the shear modulus of the elastic materials; E is the Young's modulus; ρ is the density; ν is Poisson's ratio. The last quantity is not an independent one, as E = 3K(1 − 2ν). The speed of pressure waves depends both on the pressure


id: speed-of-sound-20260505-8
file: data/en.wikipedia.org/wiki/Speed_of_sound-8.md
category: reference
title: Speed of sound
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Speed_of_sound
date_saved: 2026-05-05T10:53:25.551804+00:00
instance: kb-cron
parent: speed-of-sound-20260505-0
summary:
with check value 1550.744 m/s for T = 25 °C, S = 35 parts per thousand, z = 1,000 m. This equation has a standard error of 0.070 m/s for salinity between 25 and 40 ppt. See Technical Guides - Speed of sound in sea water for an online calculator. (The Sound Speed vs. Depth graph does not correlate directly to the MacKenzie formula. This is due to the fact that the temperature and salinity varies at different depths. When T and S are held constant, the formula itself is always increasing with depth.) Other equations for the speed of sound in sea water are accurate over a wide range of conditions, but are far more complicated, e.g., that by V. A. Del Grosso and the Chen-Millero-Li Equation. === Speed of sound in plasma === The speed of sound in a plasma for the common case that the electrons are hotter than the ions (but not too much hotter) is given by the formula (see here) c s = ( γ Z k T e m i ) 1 / 2 = ( γ Z T e μ ) 1 / 2 × 90.85 m / s , {\displaystyle c_{s}=\left({\frac


id: standard-atomic-weight-20260505-0
file: data/en.wikipedia.org/wiki/Standard_atomic_weight-0.md
category: reference
title: Standard atomic weight
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Standard_atomic_weight
date_saved: 2026-05-05T10:53:26.735765+00:00
instance: kb-cron
parent: standard-atomic-weight-20260505-0
summary:
The standard atomic weight of a chemical element (symbol Ar°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, isotope 63Cu (Ar = 62.929) constitutes 69% of the copper on Earth, the rest being 65Cu (Ar = 64.927), so A r ° ( 29 Cu ) = 0.69 × 62.929 + 0.31 × 64.927 = 63.55. {\displaystyle A_{\text{r}}{\text{°}}(_{\text{29}}{\text{Cu}})=0.69\times 62.929+0.31\times 64.927=63.55.} Relative isotopic mass is dimensionless, and so is the weighted average. It can be converted into a measure of mass (with dimension M) by multiplying it with the atomic mass constant dalton. Among various variants of the notion of atomic weight (Ar, also known as relative atomic mass) used by scientists, the standard atomic weight (Ar°) is the most common and practical. The standard atomic weight of each chemical element is determined and published by the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) based on natural, stable, terrestrial sources of the element. The definition specifies the use of samples from many representative sources from the Earth, so that the value


