Scrape wikipedia-science: 532 new, 8 updated, 560 total (kb-cron)

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data/en.wikipedia.org/wiki/Astrology_and_astronomy-0.md

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+---
+title: "Astrology and astronomy"
+chunk: 1/2
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+category: "reference"
+tags: "science, encyclopedia"
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+---
+
+Astrology and astronomy were archaically treated together (Latin: astrologia), but gradually distinguished through the Late Middle Ages into the Age of Reason. Developments in 17th century philosophy resulted in astrology and astronomy operating as independent pursuits by the 18th century.
+Whereas the academic discipline of astronomy studies observable phenomena beyond the Earth's atmosphere, astrology uses the apparent positions of celestial objects as the basis for divination.
+
+== Overview ==
+
+In pre-modern times, most cultures did not make a clear distinction between the two disciplines, putting them both together as one. In ancient Babylonia, famed for its astrology, there were not separate roles for the astronomer as predictor of celestial phenomena, and the astrologer as their interpreter; both functions were performed by the same person. In ancient Greece, pre-Socratic thinkers such as Anaximander, Xenophanes, Anaximenes, and Heraclides speculated about the nature and substance of the stars and planets. Astronomers such as Eudoxus (contemporary with Plato) observed planetary motions and cycles, and created a geocentric cosmological model that would be accepted by Aristotle. This model generally lasted until Ptolemy, who added epicycles to explain the retrograde motion of Mars. (Around 250 BC, Aristarchus of Samos postulated a proto-heliocentric theory, which would not be reconsidered for nearly two millennia (Copernicus), as Aristotle's geocentric model continued to be favored.) The Platonic school promoted the study of astronomy as a part of philosophy because the motions of the heavens demonstrate an orderly and harmonious cosmos. In the third century BC, Babylonian astrology began to make its presence felt in Greece. Astrology was criticized by Hellenistic philosophers such as the Academic Skeptic Carneades and Middle Stoic Panaetius. However, the notions of the Great Year (when all the planets complete a full cycle and return to their relative positions) and eternal recurrence were Stoic doctrines that made divination and fatalism possible.
+In the Hellenistic world, the Greek words 'astrologia' and 'astronomia' were often used interchangeably, but they were conceptually not the same. Plato taught about 'astronomia'  and stipulated that planetary phenomena should be described by a geometrical model. The first solution was proposed by Eudoxus. Aristotle favored a physical approach and adopted the word 'astrologia'. Eccentrics and epicycles came to be thought of as useful fictions. For a more general public, the distinguishing principle was not evident and either word was acceptable. For the Babylonian horoscopic practice, the words specifically used were 'apotelesma' and 'katarche', but otherwise it was subsumed under the aristotelian term 'astrologia'.
+In his compilatory work Etymologiae, Isidore of Seville noted explicitly the difference between the terms astronomy and astrology (Etymologiae, III, xxvii) and the same distinction appeared later in the texts of Arabian writers. Isidore identified the two strands entangled in the astrological discipline and called them astrologia naturalis and astrologia superstitiosa.
+Astrology was widely accepted in medieval Europe as astrological texts from Hellenistic and Arabic astrologers were translated into Latin. In the late Middle Ages, its acceptance or rejection often depended on its reception in the royal courts of Europe. Not until the time of Francis Bacon was astrology rejected as a part of scholastic metaphysics rather than empirical observation. A more definitive split between astrology and astronomy in the West took place gradually in the seventeenth and eighteenth centuries, when astrology was increasingly thought of as an occult science or superstition by the intellectual elite. The famous polymath Al-Biruni was one of the first scholars to make this distinction in the late 10th and early 11th centuries CE. He differentiated astrology from astronomy considering the former more of an art or practice and criticised its weak mathematical and scientific foundations. Because of their lengthy shared history, it sometimes happens that the two are confused with one another even today. Many contemporary astrologers, however, do not claim that astrology is a science, but think of it as a form of divination like the I-Ching, an art, or a part of a spiritual belief structure (influenced by trends such as Neoplatonism, Neopaganism, Theosophy, and Hinduism).
+
+== Distinguishing characteristics ==
+
+The primary goal of astronomy is to understand the physics of the universe. Astrologers use astronomical calculations for the positions of celestial bodies along the ecliptic and attempt to correlate celestial events (astrological aspects, sign positions) with earthly events and human affairs. Astronomers consistently use the scientific method, naturalistic presuppositions and abstract mathematical reasoning to investigate or explain phenomena in the universe. Astrologers use mystical or religious reasoning as well as traditional folklore, symbolism and superstition blended with mathematical predictions to explain phenomena in the universe. The scientific method is not consistently used by astrologers.
+Astrologers practice their discipline geocentrically and they consider the universe to be harmonious, changeless and static, while astronomers have employed the scientific method to infer that the universe is without a center and is dynamic, expanding outward per the Big Bang theory.
+Astrologers believe that the position of the stars and planets determine an individual's personality and future. Astronomers study the actual stars and planets, but have found no evidence supporting astrological theories. Psychologists study personality, and while there are many theories of personality, no mainstream theories in that field are based on astrology.  (The Myers-Briggs personality typology, based on the works of Carl Jung, has four major categories that correspond to the astrological elements of fire, air, earth, and water.  This theory of personality is used by career counselors and life coaches but not by psychologists.)
+Both astrologers and astronomers see Earth as being an integral part of the universe, that Earth and the universe are interconnected as one cosmos (not as being separate and distinct from each other). However, astrologers philosophically and mystically portray the cosmos as having a supernatural, metaphysical and divine essence that actively influences world events and the personal lives of people. Astronomers, as members of the scientific community, cannot use in their scientific articles explanations that are not derived from empirically reproducible conditions, irrespective of their personal convictions.
+
+== Historical divergence ==

data/en.wikipedia.org/wiki/Astrology_and_astronomy-1.md

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+---
+title: "Astrology and astronomy"
+chunk: 2/2
+source: "https://en.wikipedia.org/wiki/Astrology_and_astronomy"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:29.137090+00:00"
+instance: "kb-cron"
+---
+
+For a long time the funding from astrology supported some astronomical research, which was in turn used to make more accurate ephemerides for use in astrology. In Medieval Europe the word Astronomia was often used to encompass both disciplines as this included the study of astronomy and astrology jointly and without a real distinction; this was one of the original Seven Liberal Arts. Kings and other rulers generally employed court astrologers to aid them in the decision making in their kingdoms, thereby funding astronomical research. University medical students were taught astrology as it was generally used in medical practice.
+Astronomy and astrology diverged over the course of the 17th through 19th centuries. It is unclear if Copernicus practiced astrology,), but the most important astronomers before Isaac Newton were astrologers by profession—Tycho Brahe, Johannes Kepler, and Galileo Galilei.
+Also relevant here was the development of better timekeeping instruments, initially for aid in navigation; improved timekeeping made it possible to make more exact astrological predictions—predictions which could be tested, and which consistently proved to be false. By the end of the 18th century, astronomy was one of the major sciences of the Enlightenment model, using the recently codified scientific method, and was altogether distinct from astrology.
+
+== Astrology and zodiac signs in the modern age ==
+Astrology is considered by many philosophers and astronomers to be a false representation of the universe that individuals may use to associate the movement of the celestial bodies to their own ideas of human life and spirituality. Although many scholars consider astrology to be a pseudoscience, those that believe in zodiac signs and their meanings will argue the opposite, and these followers will support their claims with explanations for how and why the universe is connected to the human condition.
+The most popular and well-known form of astrology is seen in horoscopes that people are exposed to through social media, popular news outlets, and digital media. The horoscopes allow people interested in astrology and zodiac signs to associate planets like Mars to human emotions such as drive and courage, and further increase the notion that these planets and their motions have an effect on their daily lives. Although astrology was considered factual predictions in ancient science, in modern times it is used as a spiritual belief system for many people. Ancient forms of astrology often combined with astronomy, but eventually split into separate paths during the time of Copernicus, Kepler, and Galileo.
+Zodiac signs in modern times are constructed from constellations seen across the earth, and they are used to associate human emotions and tendencies with the stars and heavenly bodies. In some ways, astrology has become somewhat of a pseudo-religion, due to the emphasis put on the meanings of constellations and how they relate to each individual. One may "judge" another person based on their zodiac sign, simply because there are unique listed traits carried by each sign, which reflect on the person who it refers to.
+The signs that are attributed to individuals are based on the time of year that each individual was born in. For example, people born between about 20 April and 20 May will carry the zodiac sign of Taurus, and those born between about 23 July and 22 August carry the Leo sign. Despite the many individuals that consider zodiac astrology to be factual, many consider the horoscope meanings to be false and simply participate in this modern astrology for enjoyment. Lastly, zodiac signs and astrology in the modern era are very different from the astrology of the ancient world. The minimal technology, knowledge, and expertise of the ancient world allowed for the combination of astrology and astronomy to become the generally accepted explanation for the universe and its impact on human lives. Whereas in current times, astrology and astronomy are extremely different.
+Zodiac signs and horoscopes are a product of cultural developments (such as the internet) that allow for easy access to information on the horoscopes through social media, tabloids and news outlets that benefit from promoting these aspects of astrology. Many individuals that are interested in horoscopes are not aware that the signs and their respective dates are inaccurate, and do not have any basis in science. Due to the "trendy" nature of zodiac signs and their popularity, it is widely recognized as part of global culture.
+
+* Scorpio is not visible through the full period. Instead, the constellation Ophiuchus is visible during this time and so is a proposed 13th zodiac sign.
+
+== See also ==
+History of astrology
+History of astronomy
+Natal chart
+Panchangam
+The Sophia Centre
+Treatise on the Astrolabe
+
+== References ==
+
+== Further reading ==
+Eade, J. C. (1984). The Forgotten Sky: A Guide to Astrology in English Literature. Oxford: Clarendon Press; New York: Oxford University Press. ISBN 978-0-19-812813-7.
+Losev, A. (2012). "'Astronomy' or 'astrology': a brief history of an apparent confusion". Journal of Astronomical History and Heritage. 15 (1): 42–46. arXiv:1006.5209. Bibcode:2012JAHH...15...42L. doi:10.3724/SP.J.1440-2807.2012.01.05.
+North, John David (1988). Chaucer's Universe. Oxford: Clarendon Press.
+"What's the difference between astronomy and astrology?". American Astronomical Society. Archived from the original on 1 July 2014. Retrieved 17 August 2014.
+
+== External links ==
+The Geoffrey Chaucer Page: Astrology & Astronomy, Harvard University
+An Astronomer Looks at Astrology

data/en.wikipedia.org/wiki/Barlow's_law-0.md

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+title: "Barlow's law"
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+source: "https://en.wikipedia.org/wiki/Barlow's_law"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:30.346242+00:00"
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+---
+
+Barlow's law is an incorrect physical law proposed by Peter Barlow in 1825 to describe the ability of wires to conduct electricity. It says that the strength of the effect of electricity passing through a wire varies inversely with the square root of its length and directly with the square root of its cross-sectional area, or, in modern terminology:
+
+  
+    
+      
+        I
+        ∝
+        
+          
+            
+              A
+              L
+            
+          
+        
+        ,
+      
+    
+    {\displaystyle I\propto {\sqrt {\frac {A}{L}}},}
+  
+
+where I is electric current, A is the cross-sectional area of the wire, and L is the length of the wire. Barlow formulated his law in terms of the diameter d of a cylindrical wire.  Since A is proportional to the square of d the law becomes 
+  
+    
+      
+        I
+        ∝
+        d
+        
+          /
+        
+        
+          
+            L
+          
+        
+      
+    
+    {\displaystyle I\propto d/{\sqrt {L}}}
+  
+ for cylindrical wires.
+Barlow undertook his experiments with the aim of determining whether long-distance telegraphy was feasible and believed that he proved that it was not. The publication of Barlow's law delayed research into telegraphy for several years, until 1831 when Joseph Henry and Philip Ten Eyck constructed a circuit 1,060 feet long, which used a large battery to activate an electromagnet. Barlow did not investigate the dependence of the current strength on electric tension (that is, voltage). He endeavoured to keep this constant, but admitted there was some variation. Barlow was not entirely certain that he had found the correct law, writing "the discrepancies are rather too great to enable us to say, with confidence, that such is the law in question."
+In 1827, Georg Ohm published a different law, in which current varies inversely with the wire's length, not its square root; that is,
+
+  
+    
+      
+        I
+        ∝
+        
+          
+            1
+            
+              c
+              +
+              L
+              
+                /
+              
+              A
+            
+          
+        
+        ,
+      
+    
+    {\displaystyle I\propto {\frac {1}{c+L/A}},}
+  
+
+where 
+  
+    
+      
+        c
+      
+    
+    {\displaystyle c}
+  
+ is a constant dependent on the circuit setup. Ohm's law is now considered the correct law, and Barlow's false.
+The law Barlow proposed was not in error due to poor measurement; in fact, it fits Barlow's careful measurements quite well.  Heinrich Lenz pointed out that Ohm took into account "all the conducting resistances … of the circuit", whereas Barlow did not. Ohm explicitly included a term for what we would now call the internal resistance of the battery. Barlow did not have this term and approximated the results with a power law instead. Ohm's law in modern usage is rarely stated with this explicit term, but nevertheless an awareness of it is necessary for a full understanding of the current in a circuit.
+
+
+== References ==

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+title: "Bharat Ki Chhap"
+chunk: 1/1
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+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:31.564809+00:00"
+instance: "kb-cron"
+---
+
+Bharat Ki Chhap (Identity of India) is a 13-episode Indian TV science documentary series chronicling the history of science and technology in India from pre-historic times until the present. It was directed by filmmaker Chandita Mukherjee and funded by the Department of Science and Technology's National Council for Science and Technology Communication (NCSTC) in 1987. It was telecasted on Doordarshan every Sunday Morning. It was introduced by Professor Yash Pal.
+It projected in a pragmatic way alternative viewpoints on the subject of science as pioneered in India, in contrast with western scientific endeavours. It drew support from People's Science Movement.
+A companion book was later published by Comet Project titled Bhārat Ki Chhāp: A Companion Book to the Film Series by Chayanika Shah, Suhas Paranjape, Swatija Manorama.
+
+
+== Episodes ==
+A total of 13 episodes were released.
+
+
+== References ==

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+title: "Book of Nature"
+chunk: 1/3
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+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:33.831526+00:00"
+instance: "kb-cron"
+---
+
+The Book of Nature (Lat. liber naturae/liber mundi, Ar. kitāb takwīnī) is a religious and philosophical cosmological metaphor known from Antiquity in various cultures, and prominent in the Latin and Romance literature of the European Middle Ages. The idea of a cosmos formed by letters is already found in the fragments of Heraclitus, where it relates to the Greek concept of logos, in Plato’s Timaeus, and in Lucretius’ De rerum natura.
+The metaphor of the Book of Nature straddles the divide between religion and science, viewing nature as a readable text open to knowledge and understanding. Early theologians, such as St. Paul, believed the Book of Nature was a source of God's revelation to humankind. He believed that when read alongside sacred scripture, the "book" and the study of God's creations would lead to a knowledge of God himself. This type of revelation is often referred to as a general revelation. The concept corresponds to the early Greek philosophical concept of logos, which implies that humans, as part of a coherent universe, are capable of understanding the design of the natural world through reason. The phrase liber naturae was famously used by Galileo when writing about how "the book of nature [can become] readable and comprehensible".
+
+== History ==
+From the earliest times in known civilizations, events in the natural world were expressed through a collection of stories concerning everyday life. In ancient times, it was believed that the visible, mortal world existed alongside an upper world of spirits and gods acting through nature to create a unified and intersecting moral and natural cosmos. Humans, living in a world that was acted upon by free-acting and conspiring gods of nature, attempted to understand their world and the actions of the divine by observing and correctly interpreting natural phenomena, such as the motion and position of stars and planets. Efforts to analyze and understand divine intentions led mortals to believe that intervention and influence over godly acts were possible—either through religious persuasions, such as prayer and gifts, or through magic, which depended on sorcery and the manipulation of nature to bend the will of the gods. Humans believed they could discover divine intentions through observing or manipulating the natural world. Thus, mankind had a reason to learn more about nature.
+Around the sixth century BCE, humanity’s relationship with the deities and nature began to change. Greek philosophers, such as Thales of Miletus, no longer viewed natural phenomena as the result of omnipotent gods. Instead, natural forces resided within nature, an integral part of a created world, and appeared under certain conditions that had little to do with personal deities. The Greeks believed that natural phenomena occurred by "necessity" through intersecting chains of "cause" and "effect". Greek philosophers, however, lacked a new vocabulary to express such abstract concepts as "necessity" or "cause" and consequently used words available to them to refer metaphorically to the new philosophy of nature. As such, they began to conceptualize the natural world in more specific terms that aligned with a unique philosophy that viewed nature as immanent and where natural phenomena occurred by necessity.
+The Greek concept of nature, metaphorically expressed through the Book of Nature, gave birth to three philosophical traditions that became the wellspring for natural philosophy and early scientific thinking. Among the three traditions inspired by Plato, Aristotle, and Pythagoras, the Aristotelian corpus became a pervasive force in natural philosophy until it was challenged in early modern times. Natural philosophy, which encompassed a body of work whose purpose was to describe and explain the natural world, derived its foremost authority in the medieval era from Christian interpretations of Aristotle, in which his natural philosophy was viewed as a doctrine intended to explain natural events in terms of readily understood causes.
+Aristotle reasoned that knowledge of natural phenomena was derived by abstraction from a sensory awareness of the natural world—in short, knowledge was obtained through sensory experience. A world constructed by abstract ideas alone could not exist. In his reasoning, the structures inherent in nature are revealed through a process of abstraction, which may result in metaphysical principles that can be used to explain various natural phenomena, including their causes and effects. Events with no identifiable reason happen by chance and reside outside the boundaries of natural philosophy. The search for causal explanations became a dominant focus in natural philosophy, whose origins lay in the Book of Nature as conceived by the earliest Greek philosophers. Aristotle’s influence throughout Europe lasted centuries until the Enlightenment warranted fresh investigations of entrenched ideas. 

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+---
+title: "Book of Nature"
+chunk: 2/3
+source: "https://en.wikipedia.org/wiki/Book_of_Nature"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:33.831526+00:00"
+instance: "kb-cron"
+---
+
+== Christianity and Greek culture ==
+The Greeks constructed a view of the natural world in which all references to mythological origins and causes were removed. Greek philosophers inadvertently left the upper world vacant by abandoning ancient ties to free-acting, conspiring gods of nature. The new philosophy of nature made unseen mythological forces irrelevant. While some philosophers drifted toward atheism, others worked within the new philosophy to reconstitute the concept of a divine being. Consequently, the new outlook toward the natural world inspired the belief in one supreme force compatible with the new philosophy—in other words, monotheistic. However, the path from nature to rediscovering a divine being was uncertain. The belief in causality in nature implied an endless, interconnected chain of causation acting upon the natural world. It is presumed, however, that Greek thought denied the existence of a natural world where causality was infinite, which gave rise to the notion of "first cause", upon which the order of other causes must rely.
+The first contact between Christianity and Greek culture occurred in Athens in the first century CE. The Christian Scriptures note that within a few years of Christ’s crucifixion, Paul and Silas were debating with Epicureans and Stoics at the Areopagus. Christian theologians viewed the Greeks as a pagan culture whose philosophers were obsessed with the wonders of the material, or the natural world. Observation and explanation of natural phenomena were of little value to the Church. Consequently, early Christian theologians dismissed Greek knowledge as perishable in contrast to actual knowledge derived from sacred Scripture. At the same time, the Church Fathers struggled with questions concerning the natural world and its creation that reflected the concerns of Greek philosophers. 
+Despite their rejection of pagan thinking, the Church Fathers benefited from Greek dialectic and ontology by inheriting a technical language that could help express solutions to their concerns. As Peter Harrison observes, "In the application of the principles of pagan philosophy to the raw materials of a faith, the content of which was expressed in those documents which were to become the New Testament, we can discern the beginnings of Christian theology." Eventually, Church Fathers would recognize the value of the natural world because it provided a means of deciphering God’s work and acquiring true knowledge of Him. God was believed to have infused the material world with symbolic meaning, which, if understood by man, reveals higher spiritual truths. 
+What the Church Fathers needed, and did not inherit from the early Greek philosophers, was a method of interpreting the symbolic meanings embedded in the material world. According to Harrison, it was Church Father Origen in the third century who perfected a hermeneutical method that was first developed by the Platonists of the Alexandrian school by which the natural world could be persuaded to give up hidden meanings.
+In Christianity, early Church Fathers appeared to use the idea of a book of nature, librum naturae, as part of a two-book theology: "Among the Fathers of the Church, explicit references to the Book of Nature can be found, in St. Basil, St. Gregory of Nyssa, St. Augustine, John Cassian, St. John Chrysostom, Ephrem the Syrian, St. Maximus the Confessor". St Augustine suggested that Nature and the Bible were a two-volume set of books written by God and filled with divine knowledge.
+
+== Rediscovering the natural world ==
+
+By the twelfth century, a renewed study of nature was beginning to emerge along with the recovered works of ancient philosophers, translated from Arabic to original Greek. The writings of Aristotle were seen as being among the most important of the ancient texts and had a remarkable influence among intellectuals. Interest in the material world, in conjunction with the doctrines of Aristotle, elevated sensory experience to new levels of importance. Earlier teachings concerning the relationship between God and man’s knowledge of material things gave way to a world in which knowledge of the material world conveyed the knowledge of God. Whereas scholars and theologians once held a symbolist mentality of the natural world as expressive of spiritual realities, intellectual thinking now regarded nature as a "coherent entity which the senses could systematically investigate. The idea of nature is that of a particular ordering of natural objects, and the study of nature is the systematic investigation of that order". 
+The idea of order in nature implied a structure to the physical world whereby relationships between objects could be defined. According to Harrison, the twelfth century marked an important time in the Christian era when the world became invested with its patterns of order—patterns based on networks of likeness or similarities among material things, which led to a pre-modern knowledge of nature. It was believed that "While God has made all things that reside in the Book of Nature, certain objects in nature share similar characteristics with other objects, which delineates the sphere of nature and 'establishes the systematizing principles upon which knowledge of the natural world is based'". Nature could now be read like a book.
+
+== The birth of modern science ==

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+---
+title: "Book of Nature"
+chunk: 3/3
+source: "https://en.wikipedia.org/wiki/Book_of_Nature"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:33.831526+00:00"
+instance: "kb-cron"
+---
+
+From a single print shop in Mainz, Germany around 1440, the movable type printing-press had spread to no less than around 270 cities in Central, Western and Eastern Europe and had already produced more than 20 million volumes by the end of the 15th century. At the same time, the number of universities had grown to more than 60. By revealing a "New World" unknown to the ancients, the European encounter with the Americas specifically undermined the authority of Claudius Ptolemy, the 2nd-century scholar whose geographic and astronomical models had long been considered infallible. 
+Tycho Brahe's unprecedentedly accurate astronomical observations in the late 16th century and Galileo Galilei’s early 17th-century telescopic observations combined to turn astronomy into the first modern science. Galileo's observations ended a millenium of pre-modern astronomical orthodoxy.  Johannes Kepler used Brahe's data to discover that planets have elliptical, not circular, orbits and develop the laws of planetary motion. Because of Kepler, astronomical phenomena came to be seen as being governed by physical laws, a kind of clockwork.
+Ancient texts and doctrines were disputed, knowledge of the natural world was incomplete, interpretation of Christian Scripture was challenged, and Greek philosophy—which helped draft the Book of Nature—and Christian Scripture were viewed as fundamentally opposed. 
+The Book of Nature was acquiring greater authority for its wisdom and as an unmediated source of natural and divine knowledge. Hands-on investigations, whether of the human body, horticulture, or the stars, were encouraged. As a source of revelation, the Book of Nature remained moored to the Christian faith and occupied a prominent location in Western culture alongside the Bible. Scientific philosophers such as Robert Boyle and Sir Isaac Newton believed that nature could teach humans the breadth of work which God had carried out; Francis Bacon told his readers that they could never be too well-versed in the book of God’s Scripture or the book of God’s nature. The Book of Nature was seen as a way of learning more about God.
+
+== Two books - two worlds? ==
+The view of nature as divine revelation and the need for scientific research continued for several centuries. When the word scientist began to replace the term natural philosopher in the 1830s, the most talked-about scientific books in the UK were the eight-volume Bridgewater Treatises. These books, funded by the last Earl of Bridgewater, were written by men appointed by the Royal Society to "explore the Power, Wisdom and Goodness of Gd [sic], as manifested in the Creation".
+At that time, nature and the divine were seen to be parallel. However, the concern that the two books would eventually collide was becoming increasingly evident among scholars, natural philosophers, and theologians, who saw the possibility of two separate and incompatible worlds—one determined to possess nature, and the other determined to uphold Christian faith. Reacting to the works of scientists such as Charles Darwin and Alfred Russel Wallace some popular authors began to show that nature may not reveal God, but may show that there is no god at all, but such conclusions did not follow from the theories of natural selection. In Fact, Russel Wallace was a leading scientist and an advocate of spiritualism at the same time, and strongly believed that evolution theories represented an advance in our understanding of the book of nature. Discoveries in paleontology led many to question the Christian scriptures and other divine beliefs. Scientists engaged in physical observation of nature separated themselves from spiritual issues. In contrast, the emerging disciplines of psychology and sociology led others to see religious belief as a temporary step in a society’s development rather than a central and essential element. By 1841, Auguste Comte proposed that empirical observation was the final culmination of human society.
+
+== See also ==
+The Assayer
+Science and the Catholic Church
+Natural theology – Theology reliant on rational and empirical arguments
+Dogmatics – Theology of theoretical official truthsPages displaying short descriptions of redirect targets
+
+== Notes ==
+
+== Bibliography ==
+Dear, Peter (2009). Revolutionizing the Sciences: European Knowledge and Its Ambitions, 1500-1700. Princeton: Princeton University Press. ISBN 978-0-691-14206-7.
+Evernden, Lorne Leslie Neil. The Social Creation of Nature. Baltimore, MD: Johns Hopkins University Press, 1992.
+Harrison, Peter (26 July 2001). The Bible, Protestantism, and the Rise of Natural Science. New York: Cambridge University Press. ISBN 978-0-521-00096-3.
+Pedersen, Olaf (1992). The Book of Nature. Notre Dame, IN: Notre Dame Press. ISBN 0-268-00690-3.
+Wootton, David (2015). The Invention of Science: A New History of the Scientific Revolution. New York: Harper, an imprint of HarperCollins Publishers. ISBN 978-0-06-175952-9.
+
+== Further reading ==
+Acevedo, J. Alphanumeric Cosmology from Greek into Arabic: The Idea of Stoicheia Through the Medieval Mediterranean. Tübingen, Mohr Siebeck, 2020.
+Binde, Per. "Nature in Roman Catholic Tradition". Anthropological Quarterly 74, no. 1 (January 2001): 15-27.
+Blackwell, Richard J. Galileo, Bellarmine, and the Bible. Notre Dame: University of Notre Dame Press, 1991.
+Blumenberg, Hans. The Readability of the World. Trans. Robert Savage and David Roberts. Ithaca, Cornell University Press, 2022. ISBN 978-1-5017-6661-9.
+Eddy, Matthew, and Knight, David M. Introduction. Natural Theology. By William Paley. 1802. New York: Oxford University Press, 2006. ix-xxix.
+Eisenstein, Elizabeth L. The Printing Revolution in Early Modern Europe. New York: Cambridge University Press, 2005.
+Findlen, Paula. Possessing Nature: Museums, Collecting, and Scientific Culture in Early Modern Italy. Berkeley: University of California Press, 1996.
+Henry, John. The Scientific Revolution and the Origins of Modern Science. New York: Palgrave Macmillan, 2008.
+Kay, Lily E. Who Wrote the Book of Life?: A History of the Genetic Code. Stanford, CA: Stanford University Press, 2000.
+Kosso, Peter. Reading the book of nature: an introduction to the philosophy of science. Cambridge: Cambridge University Press, 1992.
+Nelson, Benjamin. "Certitude, and the Books of Scripture, Nature, and Conscience". In On the Roads to Modernity: Conscience, Science, and Civilizations. Selected Writings by Benjamin Nelson, edited by Toby E. Huff. Totowa, N.J.: Rowman and Littlefield, 1981.
+Seibold, J. “Liber naturae et liber scripturae: doctrina patrística-medieval, su interpretación moderna y su perspectiva actual.” Stromata, 40(1/2), 2019, pp.59-85. External link.

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+---
+title: "Bridgewater Treatises"
+chunk: 1/3
+source: "https://en.wikipedia.org/wiki/Bridgewater_Treatises"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:34.927628+00:00"
+instance: "kb-cron"
+---
+
+The Bridgewater Treatises (1833–36) are a series of eight works that were written by leading scientific figures appointed by the President of the Royal Society in fulfilment of a bequest of £8000, made by Francis Henry Egerton, 8th Earl of Bridgewater, for work on "the Power, Wisdom, and Goodness of God, as manifested in the Creation."
+Despite being voluminous and costly, the series was very widely read and discussed, becoming one of the most important contributions to Victorian literature on the relationship between religion and science.  They made such an impact that Charles Darwin began On the Origin of Species with a quotation from the Bridgewater Treatise of William Whewell.
+
+== The Bridgewater Bequest ==
+Before unexpectedly becoming the 8th Earl of Bridgewater in 1823, Francis Henry Egerton spent most of his life as an absentee parson. He published works of classical scholarship and issued others praising the historical achievements of his family, including those of his father's cousin, Francis Egerton, 3rd Duke of Bridgewater, the "father of British inland navigation."  In 1781, he was elected a Fellow of the Royal Society; after 1802 he lived mostly in Paris, where he amassed a collection of manuscripts later donated to the British Museum and gained a reputation as an eccentric. He died in February 1829, leaving a will dated 25 February 1825, in which he directed that £8000 was to be used by the President of the Royal Society to appoint a "person or persons":...to write, print, and publish, one thousand copies of a work On the Power, Wisdom, and Goodness of God, as manifested in the Creation; illustrating such work by all reasonable arguments, as, for instance, the variety and formation of God's creatures in the animal, vegetable, and mineral kingdoms; the effect of digestion, and thereby of conversion; the construction of the hand of man, and an infinite variety of other arguments: as also by discoveries, ancient and modern, in arts, sciences, and the whole extent of literature.The President of the Royal Society at the time was Davies Gilbert, who sought the assistance of the Archbishop of Canterbury, William Howley, and the Bishop of London, Charles James Blomfield, in selecting authors. Those appointed, with the titles and dates of their treatises, were:
+The Adaptation of External Nature to the Moral and Intellectual Condition of Man (1833), by Thomas Chalmers, D.D.
+On The Adaptation of External Nature to the Physical Condition of Man (1833), by John Kidd, M.D.
+Astronomy and General Physics Considered with Reference to Natural Theology (1833), by William Whewell, D.D.
+The Hand, its Mechanism and Vital Endowments as Evincing Design (1833), by Sir Charles Bell.
+Animal and Vegetable Physiology Considered with Reference to Natural Theology (1834), by Peter Mark Roget.
+Geology and Mineralogy Considered with Reference to Natural Theology (1836), by William Buckland, D.D.
+On the History, Habits and Instincts of Animals (1835), by William Kirby.
+Chemistry, Meteorology, and the Function of Digestion, Considered with Reference to Natural Theology (1834), by William Prout, M.D.
+In the midst of a movement for reform in the Royal Society and a clamour surrounding the Reform Act 1832, the administration of the bequest was widely criticized. The calibre and reputation of the authors was, however, of a high order, and they included several prominent scientific figures of the age.
+
+== The Bridgewater Treatises ==
+The eight authors appointed to write the Bridgewater Treatises were offered little guidance about what was expected of them, and the individual works were varied. In particular, while the series has sometimes been seen primarily as a contribution to natural theology, the authors did not agree about the extent to which humans could acquire knowledge of God by observation and reasoning without the aid of revealed knowledge. Instead, the series offered "a working epitome of each of the main branches of natural science, and its final impact was expected to demonstrate the higher meaning of the order of nature and [...] to 'ennoble' empirical discovery into morality."
+
+=== Clerical professors: Whewell and Chalmers ===
+The treatises of the theologically capable university professors William Whewell and Thomas Chalmers were the ones that offered the greatest theological sophistication.  In his work on "astronomy and general physics," Whewell claimed that his purpose was to "lead the friends of religion to look with confidence and pleasure on the progress of the physical sciences, by showing how admirably every advance in our knowledge of the universe harmonizes with the belief in a most wise and good God."  In particular, he argued that the scientific view that nature was "governed by laws" was not at odds with belief in a creator, an argument later used by Charles Darwin. Scottish clergyman Thomas Chalmers's treatise on "the moral and intellectual constitution of man" argued that the human conscience and the mechanism of society manifested God's moral qualities, drawing heavily on his previously published views as a Malthusian political economist. He nevertheless placed severe limits on natural theology in a final chapter on "the defects and uses of natural theology."

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+---
+title: "Bridgewater Treatises"
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+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:34.927628+00:00"
+instance: "kb-cron"
+---
+
+=== Medical practitioners: Kidd and Bell, Roget and Prout ===
+The two medical professors John Kidd and Charles Bell wrote shorter and theologically lightweight contributions. Kidd's work, on the "physical constitution of man," was claimed to be "but a moderate thousand pounds worth," Like Bell, whose limited subject was "the hand," Kidd set out to show that modern developments in anatomy did not support either materialism or the transmutation of species, instead confirming belief in the reality of divine design. The two other medical authors, Peter Mark Roget and William Prout, wrote lengthier contributions considering how the emergence of physiological laws enhanced the belief in divine design, rather than diminishing it. In his treatise on "animal and vegetable physiology," Roget argued that the laws of "philosophical anatomy" provided a grander vision of divine action. Prout's rag-bag treatise on "chemistry, meteorology, and the function of digestion" was more ambivalent, arguing that God's action was strikingly evident in the laws of chemical action, but also that many phenomena seemed to subvert the general laws.
+
+=== The Bible and science: Kirby and Buckland ===
+The final two treatises, those of William Kirby and William Buckland, both addressed the relationship of the Bible to scientific enquiry, but from very different perspectives. High Churchman Kirby's treatise on the "history, habits, and instincts of animals" began with a quotation from German naturalist Heinrich Moritz Gaede stating: "It is Bible in hand that we must enter into the august temple of nature." A follower of the view of theologian John Hutchinson (1674–1737) that the Bible contains hidden symbolic meanings, he argued that modern naturalists such as the transmutationist Jean-Baptiste Lamarck had lost their way by failing to honour the Bible. In stark contrast, the University of Oxford's Professor of Geology, William Buckland, declared in his first chapter that there was nothing in the Bible to suggest that the earth may not be ages old. Accepting the facts of geology only strengthened Christianity, he claimed, by offering new evidence of design and disproving the idea of the transmutation of species.
+Ranging across the sciences, the Bridgewater Treatises took different approaches to trying to demonstrate how science was supportive of Christianity. Taken as a whole, they tended to imply that neither natural laws nor a historical process of creation were inconsistent with Christianity. However, they were opposed to both materialism and transmutation of species.
+
+== Reception and responses ==
+The Bridgewater Treatises were published by London publisher William Pickering and while they were very expensive (they were priced between 9s.6d. and £1 10s.) they nevertheless sold very rapidly.  Buckland's treatise on geology sold a first edition of 5000 copies straight away and a second edition of the same size was immediately produced. The series was very widely reviewed and republished, and the treatises were also bought by a large number of libraries, including the libraries of the Mechanics' Institutes.  In 1836, Thomas Dibdin considered that the Bridgewater Treatises were set to "traverse the whole civilized portion of the globe." Sales tailed off in the 1840s, but the series was reissued in Henry Bohn's Scientific Library from the 1850s, with some of the treatises remaining in print in the 1880s. The Bridgewater Treatises were republished in the United States by both New York publishers Harper & Bros. and Philadelphia publishers Carey, Lea, and Blanchard.  They were translated into German by Stuttgart publisher Paul Neff, and some of the treatises appeared in French, Dutch, and Swedish.
+The works are of unequal merit and they attracted criticism from a variety of standpoints. Some religious commentators criticized them for overemphasizing natural theology, for distracting readers from the claims of the Bible, or for undermining biblical authority. Some scientific commentators attacked their particular views on science. Robert Knox, an Edinburgh surgeon and major advocate of radical morphology, referred to them as the "Bilgewater Treatises", to mock what he called the "ultra-teleological school" of anatomy. Though memorable, this phrase overemphasizes the influence of teleology in the series, at the expense of the idealism of the likes of Kirby and Roget. The series nevertheless proved very successful in conveying the impression that modern science was in harmony with Protestant Christianity and it became an emblem of that harmony in Victorian Britain and beyond.
+The great success of the series prompted authors to publish works in imitation. The most famous of these was by Charles Babbage and dubbed The Ninth Bridgewater Treatise: A Fragment (1836). As Babbage's preface states, this volume was not part of the series, but rather his own considerations on the subject written in response to the claim in Whewell's treatise that "We may thus, with the greatest propriety, deny to the mechanical philosophers and mathematicians of recent times any authority with regard to their views of the administration of the universe." Babbage drew on his own work on calculating engines to represent God as a divine programmer setting complex laws as the basis of what we think of as miracles, rather than miraculously producing new species by creative whim. A fragmentary supplement to Babbage's Fragment by Thomas Hill was published posthumously.
+
+== See also ==
+Relationship between religion and science
+Natural theology
+
+== References ==

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+---
+title: "Bridgewater Treatises"
+chunk: 3/3
+source: "https://en.wikipedia.org/wiki/Bridgewater_Treatises"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:34.927628+00:00"
+instance: "kb-cron"
+---
+
+== Further reading ==
+Addinall, Peter (1991). Philosophy and Biblical Interpretation: A Study in Nineteenth-Century Conflict. Cambridge: Cambridge University Press.
+Alexander, Denis R.; Numbers, Ronald L. (2010). Biology and Ideology from Descartes to Dawkins. University of Chicago Press. ISBN 978-0-226-60842-6.
+"Authors of the Bridgewater Treatises (act. c. 1833–1836)". Oxford Dictionary of National Biography. doi:10.1093/ref:odnb/96360. Retrieved 2022-09-12.
+Brock, W. H. (1966). "The Selection of the Authors of the Bridgewater Treatises". Notes and Records of the Royal Society of London. 21 (2): 162–179. ISSN 0035-9149.
+Clark, John F. M. (2009). Bugs and the Victorians. Yale University Press. ISBN 978-0-300-15091-9.
+Desmond, Adrian. The Politics of Evolution: Morphology, Medicine, and Reform in Radical London. University of Chicago Press. ISBN 978-0-226-14453-5.
+Gillispie, Charles Coulston (1996). Genesis and Geology: A Study in the Relations of Scientific Thought, Natural Theology, and Social Opinion in Great Britain, 1790-1850. Harvard University Press. ISBN 978-0-674-34481-5.
+Hilton, Boyd (1988). The Age of Atonement: The Influence of Evangelicalism on Social and Economic Thought, 1795-1865. Clarendon Press. ISBN 978-0-19-820107-6.
+Rehbock, Philip F. (1983). The Philosophical Naturalists: Themes in Early Nineteenth-century British Biology. University of Wisconsin Press. ISBN 978-0-299-09430-0.
+Robson, John M. "The Fiat and Finger of God: The Bridgewater Treatises". In Helmstadter, Richard J.; Lightman, Bernard V. (eds.). Victorian Faith in Crisis: Essays on Continuity and Change in Nineteenth-Century Religious Belief. Stanford, CA: Stanford University Press. ISBN 978-0-8047-1602-4.
+Rupke, Nicolaas A. (1983). ISBN 978-0-19-822907-0.
+Snyder, Laura J. (2011-02-22). The Philosophical Breakfast Club: Four Remarkable Friends Who Transformed Science and Changed the World. Crown. ISBN 978-0-307-71617-0.
+Spurway, Neil. Laws of Nature, Laws of God?: Proceedings of the Science and Religion Forum Conference, 2014. Newcastle-upon-Tyne: Cambridge Scholars Publishing. pp. 91–114. ISBN 978-1-4438-8303-0.
+Topham, Jonathan R. (1992). "Science and Popular Education in the 1830s: The Role of the "Bridgewater Treatises"". The British Journal for the History of Science. 25 (4): 397–430. ISSN 0007-0874.
+Topham, Jonathan R. (1993). 'An infinite variety of arguments': the Bridgewater Treatises and British natural theology in the 1830s (Ph.D. thesis). University of Lancaster.
+Topham, Jonathan R. (1998). "Beyond the "Common Context": The Production and Reading of the Bridgewater Treatises". Isis. 89 (2): 233–262. ISSN 0021-1753.
+Topham, Jonathan R. (2022). Reading the Book of Nature: How Eight Bestsellers Reconnected Christianity and the Sciences on the Eve of the Victorian Age, University of Chicago Press; ISBN 978-0-226-81576-3
+Young, Robert (1985). Darwin's Metaphor: Nature's Place in Victorian Culture. Cambridge: Cambridge University Press.

data/en.wikipedia.org/wiki/Charles_Babbage's_Saturday_night_soirées-0.md

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+---
+title: "Charles Babbage's Saturday night soirées"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Charles_Babbage's_Saturday_night_soirées"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:36.039917+00:00"
+instance: "kb-cron"
+---
+
+Charles Babbage's Saturday night soirées were gatherings held by the mathematician and inventor Charles Babbage at his home in Dorset Street, Marylebone, London from 1828 and into the 1840s. The soirées were attended by the cultural elite of the time.
+
+
+== Scientific soirées ==
+
+Babbage left England when his wife and father died in 1827. On his return in 1828, now in possession of a considerable inheritance, he began to host Saturday evening parties. The science historian James A. Secord describes the parties as "scientific soirées". Secord writes that Babbage imported the idea from France, and once established, such soirées "became one of the chief ways in which scientific discussion could take place on a more sustained basis within polite society."
+In her autobiography, the English writer and sociologist Harriet Martineau wrote: "All were eager to go to his glorious soirées and I always thought he appeared to great advantage as a host. His patience in explaining his machine in those days was really exemplary."
+According to biographers Bruce Collier and James H. MacLachlan, "Babbage was a bon vivant with a love of dining out and socialising. He sparkled as a host and raconteur. His Saturday soirées were glittering events attended by the social and intellectual elite of London."
+
+
+== Guests ==
+Hundreds of prominent people attended the soirées, including Ada Lovelace, Lady Byron, Arthur Wellesley, 1st Duke of Wellington, Charles Darwin and Emma Darwin, Charles Dickens, Michael Faraday, Sophia Elizabeth De Morgan, Mary Somerville, Harriet Martineau, photographic inventor Henry Fox Talbot, the actor William Macready, the composer Felix Mendelssohn, the historian Thomas Babington Macaulay, telegraph inventor Charles Wheatstone, the French philosopher Alexis de Tocqueville, geologist Charles Lyell and his wife Mary Lyell, Mary's sister Frances, the Belgian ambassador Sylvain Van de Weyer, electrical inventor Andrew Crosse and many others. According to C. R. Keeler, up to 200-300 people might attend one evening event.
+
+
+== Attractions ==
+A demo of Babbage's unfinished Difference engine was on display for guests at some of the gatherings. He also displayed a mechanical dancer. In her autobiography, Harriet Martineau describes Babbage's disappointment at his guests being more interested in this dancing doll - a toy - than in his demo of a computing machine.
+
+
+== Influence ==
+Ada Lovelace (then Ada Byron) first met Charles Babbage when her mother took her to one of his soirées on 5 June 1833, and the meeting led to a lifelong friendship and collaboration, culminating in Lovelace's notes on the Analytical engine.
+
+
+== References ==

data/en.wikipedia.org/wiki/History_of_chemistry-0.md

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+---
+title: "History of chemistry"
+chunk: 1/20
+source: "https://en.wikipedia.org/wiki/History_of_chemistry"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:38.639255+00:00"
+instance: "kb-cron"
+---
+
+The history of chemistry represents a time span from ancient history to the present. By 1000 BC, civilizations used technologies that would eventually form the basis of the various branches of chemistry. Examples include the discovery of fire, extracting metals from ores, making pottery and glazes, fermenting beer and wine, extracting chemicals from plants for medicine and perfume, rendering fat into soap, making glass,
+and making alloys like bronze.
+The protoscience of chemistry, alchemy, was unsuccessful in explaining the nature of matter and its transformations. However, by performing experiments and recording the results, alchemists set the stage for modern chemistry. The history of chemistry is intertwined with the history of thermodynamics, especially through the work of Willard Gibbs.
+
+== Ancient history ==
+
+=== Early humans ===
+
+==== Fire ====
+
+Arguably the first chemical reaction used in a controlled manner was fire. However, for millennia fire was seen simply as a mystical force that could transform one substance into another (burning wood, or boiling water) while producing heat and light. Fire affected many aspects of early societies. These ranged from the simplest facets of everyday life, such as cooking and habitat heating and lighting, to more advanced uses, such as making pottery and bricks and melting of metals to make tools. It was fire that led to the discovery of glass and the purification of metals; this was followed by the rise of metallurgy.
+
+==== Paint ====
+
+A 100,000-year-old ochre-processing workshop was found at Blombos Cave in South Africa. It indicates that early humans had an elementary knowledge of mineral processing. Paintings drawn by early humans consisting of early humans mixing animal blood with other liquids found on cave walls also indicate a small knowledge of chemistry.
+
+=== Early metallurgy ===
+
+The earliest recorded metal employed by humans seems to be gold, which can be found free or "native". Small amounts of natural gold have been found in Spanish caves used during the late Paleolithic period, around 40,000 BC. The earliest gold metallurgy is known from the Varna culture in Bulgaria, dating from c. 4600 BC.
+Silver, copper, tin and meteoric iron can also be found native, allowing a limited amount of metalworking in ancient cultures. Egyptian weapons made from meteoric iron in about 3000 BC were highly prized as "daggers from Heaven".
+During the early stages of metallurgy, methods of purification of metals were sought, and gold, known in ancient Egypt as early as 2900 BC, became a precious metal.
+
+=== Bronze Age ===
+
+==== Tin, lead, and copper smelting ====
+Certain metals can be recovered from their ores by simply heating the rocks in a fire: notably tin, lead and (at a higher temperature) copper. This process is known as smelting. The first evidence of this extractive metallurgy dates from the 6th and 5th millennia BC, and was found in the archaeological sites of the Vinča culture, Majdanpek, Jarmovac and Pločnik in Serbia. The earliest copper smelting is found at the Belovode site; these examples include a copper axe from 5500 BC. Other signs of early metals are found from the third millennium BC in places like Palmela (Portugal), Los Millares (Spain), and Stonehenge (United Kingdom). However, as often happens in the study of prehistoric times, the ultimate beginnings cannot be clearly defined and new discoveries are ongoing.
+
+==== Bronze ====
+These first metals were single elements, or else combinations as naturally occurred. By combining copper and tin, a superior metal could be made, an alloy called bronze. This was a major technological shift that began the Bronze Age about 3500 BC. The Bronze Age was a period in human cultural development when the most advanced metalworking (at least in systematic and widespread use) included techniques for smelting copper and tin from naturally occurring outcroppings of copper ores, and then smelting those ores to cast bronze. These naturally occurring ores typically included arsenic as a common impurity. Copper/tin ores are rare, as reflected in the absence of tin bronzes in western Asia before 3000 BC.
+After the Bronze Age, the history of metallurgy was marked by armies seeking better weaponry. States in Eurasia prospered when they made the superior alloys, which, in turn, made better armor and better weapons. 
+The Chinese are credited with the first ever use of Chromium to prevent rusting. Modern archaeologists discovered that bronze-tipped crossbow bolts at the tomb of Qin Shi Huang showed no sign of corrosion after more than 2,000 years, because they had been coated in chromium. Chromium was not used anywhere else until the experiments of French pharmacist and chemist Louis Nicolas Vauquelin (1763–1829) in the late 1790s. In multiple Warring States period tombs, sharp swords and other weapons were also found to be coated with 10 to 15 micrometers of chromium oxide, which left them in pristine condition to this day.
+Significant progress in metallurgy and alchemy was also made in ancient India.
+
+=== Iron Age ===

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+---
+title: "History of chemistry"
+chunk: 2/20
+source: "https://en.wikipedia.org/wiki/History_of_chemistry"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:38.639255+00:00"
+instance: "kb-cron"
+---
+
+==== Ferrous metallurgy ====
+The extraction of iron from its ore into a workable metal is much more difficult than copper or tin. While iron is not better suited for tools than bronze (until steel was discovered), iron ore is much more abundant and common than either copper or tin, and therefore more often available locally, with no need to trade for it.
+Iron working appears to have been invented by the Hittites in about 1200 BC, beginning the Iron Age. The secret of extracting and working iron was a key factor in the success of the Philistines.
+Cast iron smithing as well as the innovation of the Blast Furnace and Cupola furnace was invented in ancient China, during the Warring States period when armies sought to develop better weaponry and armor in state-armories. Many other applications, practices, and devices associated with or involved in metallurgy were also established in ancient China, with the innovations of hydraulic-powered trip hammers, and double-acting piston bellows.
+The Iron Age is named after the advent of iron working (ferrous metallurgy). Historical developments in ferrous metallurgy can be found in a wide variety of past cultures and civilizations. These include the ancient and medieval kingdoms and empires of the Middle East and Near East, ancient Iran, ancient Egypt, ancient Nubia, and Anatolia (Turkey), Ancient Nok, Carthage, the Greeks and Romans of ancient Europe, medieval Europe, ancient and medieval China, ancient and medieval India, ancient and medieval Japan, amongst others.
+
+=== Classical antiquity and atomism ===
+
+Philosophical attempts to rationalize why different substances have different properties, such as color, density, smell; exist in different states, such as solid, liquid, or gas; and react in a different manner when exposed to environments, for example temperature changes in fire or water, led ancient philosophers to postulate the first theories on nature and chemistry. The history of such philosophical theories that relate to chemistry can likely be traced back to every single ancient civilization. The common aspect in all these theories was the attempt to identify a small number of primary classical elements that make up all the various substances in nature. Substances like air, water, and soil/earth, energy forms, such as fire and light, and more abstract concepts such as thoughts, aether, and heaven, were common in ancient civilizations even in the absence of any cross-fertilization: for example ancient Greek, Indian, Mayan, and Chinese philosophies all considered air, water, earth and fire as primary elements.
+
+==== Ancient world ====
+Around 420 BC, Empedocles stated that all matter is made up of four elemental substances: earth, fire, air and water. The early theory of atomism can be traced back to ancient Greece. Greek atomism was made popular by the Greek philosopher Democritus, who declared that matter is composed of indivisible and indestructible particles called "atomos" around 380 BC. Earlier, Leucippus also declared that atoms were the most indivisible part of matter. This coincided with a similar declaration by the Indian philosopher Kanada in his Vaisheshika sutras around the same time period. Aristotle opposed the existence of atoms in 330 BC. A Greek text attributed to Polybus the physician (ca. 380 BC) argued that the human body is composed of four humours instead. Epicurus (fl. 300 BC) postulated a universe of indestructible atoms in which man himself is responsible for achieving a balanced life.
+With the goal of explaining Epicurean philosophy to a Roman audience, the Roman poet and philosopher Lucretius wrote De rerum natura (On the Nature of Things) in the middle of the first century BC. In the work, Lucretius presents the principles of atomism; the nature of the mind and soul; explanations of sensation and thought; the development of the world and its phenomena; and explains a variety of celestial and terrestrial phenomena.
+The earliest alchemists in the Western tradition seemed to have come from Greco-Roman Egypt in the first centuries AD. In addition to technical work, many of them invented chemical apparatuses. The bain-marie, or water bath, is named for Mary the Jewess. Her work also gives the first descriptions of the tribikos and kerotakis. Cleopatra the Alchemist described furnaces and has been credited with the invention of the alembic. Later, Zosimos of Panopolis wrote books on alchemy, which he called cheirokmeta, the Greek word for "things made by hand." These works include many references to recipes and procedures, as well as descriptions of instruments. Much of the early development of purification methods were described earlier by Pliny the Elder in his Naturalis Historia. He tried to explain those methods, as well as making acute observations of the state of many minerals.
+
+== Medieval alchemy ==
+
+The elemental system used in medieval alchemy was developed primarily by Jābir ibn Hayyān and was rooted in the classical elements of Greek tradition. His system consisted of the four Aristotelian elements of air, earth, fire, and water in addition to two philosophical elements: sulphur, characterizing the principle of combustibility, "the stone which burns"; and mercury, characterizing the principle of metallic properties. They were seen by early alchemists as idealized expressions of irreducible components of the universe and are of larger consideration within philosophical alchemy.
+The three metallic principles (sulphur to flammability or combustion, mercury to volatility and stability, and salt to solidity) became the tria prima of the Swiss alchemist Paracelsus. He reasoned that Aristotle's four-element theory appeared in bodies as three principles. Paracelsus saw these principles as fundamental and justified them by recourse to the description of how wood burns in fire. Mercury included the cohesive principle, so that when it left the wood (in smoke) the wood fell apart. Smoke described the volatility (the mercurial principle), the heat-giving flames described flammability (sulphur), and the remnant ash described solidity (salt).
+
+=== The philosopher's stone ===

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+
+British chemist and physicist William Crookes is noted for his cathode ray studies, fundamental in the development of atomic physics. His researches on electrical discharges through a rarefied gas led him to observe the dark space around the cathode, now called the Crookes dark space. He demonstrated that cathode rays travel in straight lines and produce phosphorescence and heat when they strike certain materials. A pioneer of vacuum tubes, Crookes invented the Crookes tube – an early experimental discharge tube, with partial vacuum with which he studied the behavior of cathode rays. With the introduction of spectrum analysis by Robert Bunsen and Gustav Kirchhoff (1859–1860), Crookes applied the new technique to the study of selenium compounds. Bunsen and Kirchhoff had previously used spectroscopy as a means of chemical analysis to discover caesium and rubidium. In 1861, Crookes used this process to discover thallium in some seleniferous deposits. He continued work on that new element, isolated it, studied its properties, and in 1873 determined its atomic weight. During his studies of thallium, Crookes discovered the principle of the Crookes radiometer, a device that converts light radiation into rotary motion. The principle of this radiometer has found numerous applications in the development of sensitive measuring instruments.
+In 1862, Alexander Parkes exhibited Parkesine, one of the earliest synthetic polymers, at the International Exhibition in London. This discovery formed the foundation of the modern plastics industry. In 1864, Cato Maximilian Guldberg and Peter Waage, building on Claude Louis Berthollet's ideas, proposed the law of mass action. In 1865, Johann Josef Loschmidt determined the number of molecules in a mole, later named Avogadro's number.
+In 1865, August Kekulé, based partially on the work of Loschmidt and others, established the structure of benzene as a six carbon ring with alternating single and double bonds. Kekulé's novel proposal for benzene's cyclic structure was much contested but was never replaced by a superior theory. This theory provided the scientific basis for the dramatic expansion of the German chemical industry in the last third of the 19th century.  Kekulé is also famous for having clarified the nature of aromatic compounds, which are compounds based on the benzene molecule. In 1865, Adolf von Baeyer began work on indigo dye, a milestone in modern industrial organic chemistry which revolutionized the dye industry.
+Swedish chemist and inventor Alfred Nobel found that when nitroglycerin was incorporated in an absorbent inert substance like kieselguhr (diatomaceous earth) it became safer and more convenient to handle, and this mixture he patented in 1867 as dynamite. Nobel later on combined nitroglycerin with various nitrocellulose compounds, similar to collodion, but settled on a more efficient recipe combining another nitrate explosive, and obtained a transparent, jelly-like substance, which was a more powerful explosive than dynamite. Gelignite, or blasting gelatin, as it was named, was patented in 1876; and was followed by a host of similar combinations, modified by the addition of potassium nitrate and various other substances.
+
+=== Mendeleev's periodic table ===

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+
+An important breakthrough in making sense of the list of known chemical elements (as well as in understanding the internal structure of atoms) was Dmitri Mendeleev's development of the first modern periodic table, or the periodic classification of the elements. Mendeleev, a Russian chemist, felt that there was some type of order to the elements and he spent more than thirteen years of his life collecting data and assembling the concept, initially with the idea of resolving some of the disorder in the field for his students. Mendeleev found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements. Mendeleev's law allowed him to build up a systematic periodic table of all the 66 elements then known based on atomic mass, which he published in Principles of Chemistry in 1869. His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties.
+Mendeleev had such faith in the validity of the periodic law that he proposed changes to the generally accepted values for the atomic weight of a few elements and, in his version of the periodic table of 1871, predicted the locations within the table of unknown elements together with their properties. He even predicted the likely properties of three yet-to-be-discovered elements, which he called ekaboron (Eb), ekaaluminium (Ea), and ekasilicon (Es), which proved to be good predictors of the properties of scandium, gallium, and germanium, respectively, which each fill the spot in the periodic table assigned by Mendeleev.
+At first the periodic system did not raise interest among chemists. However, with the discovery of the predicted elements, notably gallium in 1875, scandium in 1879, and germanium in 1886, it began to win wide acceptance. The subsequent proof of many of his predictions within his lifetime brought fame to Mendeleev as the founder of the periodic law. This organization surpassed earlier attempts at classification by Alexandre-Émile Béguyer de Chancourtois, who published the telluric helix, an early, three-dimensional version of the periodic table of the elements in 1862, John Newlands, who proposed the law of octaves (a precursor to the periodic law) in 1864, and Lothar Meyer, who developed an early version of the periodic table with 28 elements organized by valence in 1864. Mendeleev's table did not include any of the noble gases, however, which had not yet been discovered. Gradually the periodic law and table became the framework for a great part of chemical theory. By the time Mendeleev died in 1907, he enjoyed international recognition and had received distinctions and awards from many countries.
+In 1873, Jacobus Henricus van 't Hoff and Joseph Achille Le Bel, working independently, developed a model of chemical bonding that explained the chirality experiments of Pasteur and provided a physical cause for optical activity in chiral compounds. van 't Hoff's publication, called Voorstel tot Uitbreiding der Tegenwoordige in de Scheikunde gebruikte Structuurformules in de Ruimte, etc. (Proposal for the development of 3-dimensional chemical structural formulae) and consisting of twelve pages of text and one page of diagrams, gave the impetus to the development of stereochemistry. The concept of the "asymmetrical carbon atom", dealt with in this publication, supplied an explanation of the occurrence of numerous isomers, inexplicable by means of the then current structural formulae. At the same time he pointed out the existence of relationship between optical activity and the presence of an asymmetrical carbon atom.
+
+=== Josiah Willard Gibbs ===

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+
+American mathematical physicist J. Willard Gibbs's work on the applications of thermodynamics was instrumental in transforming physical chemistry into a rigorous deductive science. During the years from 1876 to 1878, Gibbs worked on the principles of thermodynamics, applying them to the complex processes involved in chemical reactions. He discovered the concept of chemical potential, or the "fuel" that makes chemical reactions work. In 1876 he published his most famous contribution, "On the Equilibrium of Heterogeneous Substances", a compilation of his work on thermodynamics and physical chemistry which laid out the concept of free energy to explain the physical basis of chemical equilibria. In these essays were the beginnings of Gibbs' theories of phases of matter: he considered each state of matter a phase, and each substance a component. Gibbs took all of the variables involved in a chemical reaction – temperature, pressure, energy, volume, and entropy – and included them in one simple equation known as Gibbs' phase rule.
+Within this paper was perhaps his most outstanding contribution, the introduction of the concept of free energy, now universally called Gibbs free energy in his honor. The Gibbs free energy relates the tendency of a physical or chemical system to simultaneously lower its energy and increase its disorder, or entropy, in a spontaneous natural process. Gibbs's approach allows a researcher to calculate the change in free energy in the process, such as in a chemical reaction, and how fast it will happen. Since virtually all chemical processes and many physical ones involve such changes, his work has significantly impacted both the theoretical and experiential aspects of these sciences. In 1877, Ludwig Boltzmann established statistical derivations of many important physical and chemical concepts, including entropy, and distributions of molecular velocities in the gas phase. Together with Boltzmann and James Clerk Maxwell, Gibbs created a new branch of theoretical physics called statistical mechanics (a term that he coined), explaining the laws of thermodynamics as consequences of the statistical properties of large ensembles of particles. Gibbs also worked on the application of Maxwell's equations to problems in physical optics. Gibbs's derivation of the phenomenological laws of thermodynamics from the statistical properties of systems with many particles was presented in his highly influential textbook Elementary Principles in Statistical Mechanics, published in 1902, a year before his death. In that work, Gibbs reviewed the relationship between the laws of thermodynamics and the statistical theory of molecular motions. The overshooting of the original function by partial sums of Fourier series at points of discontinuity is known as the Gibbs phenomenon.
+
+=== Late 19th century ===
+
+==== Carl von Linde and the modern chemical process ====

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+
+German engineer Carl von Linde's invention of a continuous process of liquefying gases in large quantities formed a basis for the modern technology of refrigeration and provided both impetus and means for conducting scientific research at low temperatures and very high vacuums. He developed a dimethyl ether refrigerator (1874) and an ammonia refrigerator (1876). Though other refrigeration units had been developed earlier, Linde's were the first to be designed with the aim of precise calculations of efficiency. In 1895 he set up a large-scale plant for the production of liquid air. Six years later he developed a method for separating pure liquid oxygen from liquid air that resulted in widespread industrial conversion to processes utilizing oxygen (e.g., in steel manufacture). He founded the Linde plc, the world's largest industrial gas company by market share and revenue.
+In 1883, Svante Arrhenius developed an ion theory to explain conductivity in electrolytes. In 1884, Jacobus Henricus van 't Hoff published Études de Dynamique chimique (Studies in Dynamic Chemistry), a seminal study on chemical kinetics. In this work, van 't Hoff entered for the first time the field of physical chemistry. Of great importance was his development of the general thermodynamic relationship between the heat of conversion and the displacement of the equilibrium as a result of temperature variation. At constant volume, the equilibrium in a system will tend to shift in such a direction as to oppose the temperature change which is imposed upon the system. Thus, lowering the temperature results in heat development while increasing the temperature results in heat absorption. This principle of mobile equilibrium was subsequently (1885) put in a general form by Henry Louis Le Chatelier, who extended the principle to include compensation, by change of volume, for imposed pressure changes. The van 't Hoff-Le Chatelier principle, or simply Le Chatelier's principle, explains the response of dynamic chemical equilibria to external stresses.
+In 1884, Hermann Emil Fischer proposed the structure of purine, a key structure in many biomolecules, which he later synthesized in 1898. He also began work on the chemistry of glucose and related sugars. In 1885, Eugen Goldstein named the cathode ray, later discovered to be composed of electrons, and the canal ray, later discovered to be positive hydrogen ions that had been stripped of their electrons in a cathode-ray tube; these would later be named protons. The year 1885 also saw the publishing of J. H. van 't Hoff's L'Équilibre chimique dans les Systèmes gazeux ou dissous à I'État dilué (Chemical equilibria in gaseous systems or strongly diluted solutions), which dealt with this theory of dilute solutions. Here he demonstrated that the "osmotic pressure" in solutions which are sufficiently dilute is proportionate to the concentration and the absolute temperature so that this pressure can be represented by a formula that only deviates from the formula for gas pressure by a coefficient i. He also determined the value of i by various methods, for example by means of the vapor pressure and François-Marie Raoult's results on the lowering of the freezing point. Thus van 't Hoff was able to prove that thermodynamic laws are not only valid for gases, but also for dilute solutions. His pressure laws, given general validity by the electrolytic dissociation theory of Arrhenius (1884–1887) – the first foreigner who came to work with him in Amsterdam (1888) – are considered the most comprehensive and important in the realm of natural sciences. In 1893, Alfred Werner discovered the octahedral structure of cobalt complexes, thus establishing the field of coordination chemistry.
+
+==== Ramsay's discovery of the noble gases ====
+
+The most celebrated discoveries of Scottish chemist William Ramsay were made in inorganic chemistry. Ramsay was intrigued by the British physicist John Strutt, 3rd Baron Rayleigh's 1892 discovery that the atomic weight of nitrogen found in chemical compounds was lower than that of nitrogen found in the atmosphere. He ascribed this discrepancy to a light gas included in chemical compounds of nitrogen, while Ramsay suspected a hitherto undiscovered heavy gas in atmospheric nitrogen. Using two different methods to remove all known gases from air, Ramsay and Lord Rayleigh were able to announce in 1894 that they had found a monatomic, chemically inert gaseous element that constituted nearly 1 percent of the atmosphere; they named it argon.
+
+The following year, Ramsay liberated another inert gas from a mineral called cleveite; this proved to be helium, previously known only in the solar spectrum. In his book The Gases of the Atmosphere (1896), Ramsay showed that the positions of helium and argon in the periodic table of elements indicated that at least three more noble gases might exist. In 1898 Ramsay and the British chemist Morris W. Travers isolated these elements—called neon, krypton, and xenon—from air and brought them to a liquid state at low temperature and high pressure. Sir William Ramsay worked with Frederick Soddy to demonstrate, in 1903, that alpha particles (helium nuclei) were continually produced during the radioactive decay of a sample of radium. Ramsay was awarded the 1904 Nobel Prize for Chemistry in recognition of "services in the discovery of the inert gaseous elements in the air, and his determination of their place in the periodic system."
+In 1897, J. J. Thomson discovered the electron using the cathode-ray tube. In 1898, Wilhelm Wien demonstrated that canal rays (streams of positive ions) can be deflected by magnetic fields and that the amount of deflection is proportional to the mass-to-charge ratio. This discovery would lead to the analytical technique known as mass spectrometry in 1912.
+
+==== Marie and Pierre Curie ====

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+Marie Skłodowska-Curie was a Polish-born French physicist and chemist who is famous for her pioneering research on radioactivity. She and her husband are considered to have laid the cornerstone of the nuclear age with their research on radioactivity. Marie was fascinated with the work of Henri Becquerel, a French physicist who discovered in 1896 that uranium casts off rays similar to the X-rays discovered by Wilhelm Röntgen. Marie Curie began studying uranium in late 1897 and theorized, according to a 1904 article she wrote for Century magazine, "that the emission of rays by the compounds of uranium is a property of the metal itself—that it is an atomic property of the element uranium independent of its chemical or physical state." Curie took Becquerel's work a few steps further, conducting her own experiments on uranium rays. She discovered that the rays remained constant, no matter the condition or form of the uranium. The rays, she theorized, came from the element's atomic structure. This revolutionary idea created the field of atomic physics and the Curies coined the word radioactivity to describe the phenomenon.
+
+Pierre and Marie further explored radioactivity by working to separate the substances in uranium ores and then using the electrometer to make radiation measurements to 'trace' the minute amount of unknown radioactive element among the fractions that resulted. Working with the mineral pitchblende, the pair discovered a new radioactive element in 1898. They named the element polonium, after Marie's native country of Poland. On December 21, 1898, the Curies detected the presence of another radioactive material in the pitchblende. They presented this finding to the French Academy of Sciences on December 26, proposing that the new element be called radium. The Curies then went to work isolating polonium and radium from naturally occurring compounds to prove that they were new elements. In 1902, the Curies announced that they had produced a decigram of pure radium, demonstrating its existence as a unique chemical element. While it took three years for them to isolate radium, they were never able to isolate polonium. Along with the discovery of two new elements and finding techniques for isolating radioactive isotopes, Curie oversaw the world's first studies into the treatment of neoplasms, using radioactive isotopes. With Henri Becquerel and her husband, Pierre Curie, she was awarded the 1903 Nobel Prize for Physics. She was the sole winner of the 1911 Nobel Prize for Chemistry. She was the first woman to win a Nobel Prize, and she is the only woman to win the award in two different fields.
+While working with Marie to extract pure substances from ores, an undertaking that really required industrial resources but that they achieved in relatively primitive conditions, Pierre himself concentrated on the physical study (including luminous and chemical effects) of the new radiations. Through the action of magnetic fields on the rays given out by the radium, he proved the existence of particles that were electrically positive, negative, and neutral; these Ernest Rutherford was afterward to call alpha, beta, and gamma rays. Pierre then studied these radiations by calorimetry and also observed the physiological effects of radium, thus opening the way to radium therapy. Among Pierre Curie's discoveries were that ferromagnetic substances exhibited a critical temperature transition, above which the substances lost their ferromagnetic behavior – this is known as the "Curie point." He was elected to the Academy of Sciences (1905), having in 1903 jointly with Marie received the Royal Society's prestigious Davy Medal and jointly with her and Becquerel the Nobel Prize for Physics. He was run over by a carriage in the rue Dauphine in Paris in 1906 and died instantly. His complete works were published in 1908.
+
+==== Ernest Rutherford ====
+
+New Zealand-born chemist and physicist Ernest Rutherford is considered to be "the father of nuclear physics." Rutherford is best known for devising the names alpha, beta, and gamma to classify various forms of radioactive "rays" which were poorly understood at his time (alpha and beta rays are particle beams, while gamma rays are a form of high-energy electromagnetic radiation). Rutherford deflected alpha rays with both electric and magnetic fields in 1903. Working with Frederick Soddy, Rutherford explained that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions.

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+He also observed that the intensity of radioactivity of a radioactive element decreases over a unique and regular amount of time until a point of stability, and he named the halving time the "half-life". In 1901 and 1902 he worked with Frederick Soddy to prove that atoms of one radioactive element would spontaneously turn into another, by expelling a piece of the atom at high velocity. In 1906 at the University of Manchester, Rutherford oversaw an experiment conducted by his students Hans Geiger (known for the Geiger counter) and Ernest Marsden. In the Geiger–Marsden experiment, a beam of alpha particles, generated by the radioactive decay of radon, was directed normally onto a sheet of very thin gold foil in an evacuated chamber. Under the prevailing plum pudding model, the alpha particles should all have passed through the foil and hit the detector screen, or have been deflected by, at most, a few degrees.
+However, the actual results surprised Rutherford. Although many of the alpha particles did pass through as expected, many others were deflected at small angles while others were reflected back to the alpha source. They observed that a very small percentage of particles were deflected through angles much larger than 90 degrees. The gold foil experiment showed large deflections for a small fraction of incident particles. Rutherford realized that, because some of the alpha particles were deflected or reflected, the atom had a concentrated centre of positive charge and of relatively large mass – Rutherford later termed this positive center the "atomic nucleus". The alpha particles had either hit the positive centre directly or passed by it close enough to be affected by its positive charge. Since many other particles passed through the gold foil, the positive centre would have to be a relatively small size compared to the rest of the atom – meaning that the atom is mostly open space. From his results, Rutherford developed a model of the atom that was similar to the Solar System, known as the Rutherford model. Like planets, electrons orbited a central, Sun-like nucleus. For his work with radiation and the atomic nucleus, Rutherford received the 1908 Nobel Prize in Chemistry.
+
+== 20th century ==
+
+In 1903, Mikhail Tsvet invented chromatography, an important analytic technique. In 1904, Hantaro Nagaoka proposed an early nuclear model of the atom, where electrons orbit a dense massive nucleus. In 1905, Fritz Haber and Carl Bosch developed the Haber process for making ammonia, a milestone in industrial chemistry with deep consequences in agriculture. The Haber process, or Haber–Bosch process, combined nitrogen and hydrogen to form ammonia in industrial quantities for the production of fertilizer and munitions. The food production for half the world's current population depends on this method for producing fertilizer. Haber, along with Max Born, proposed the Born–Haber cycle as a method for evaluating the lattice energy of an ionic solid. Haber has also been described as the "father of chemical warfare" for his work developing and deploying chlorine and other poisonous gases during World War I.
+
+In 1905, Albert Einstein explained Brownian motion in a way that definitively proved atomic theory. Leo Baekeland invented bakelite, one of the first commercially successful plastics. In 1909, American physicist Robert Andrews Millikan – who had studied in Europe under Walther Nernst and Max Planck – measured the charge of individual electrons with unprecedented accuracy through the oil drop experiment, in which he measured the electric charges on tiny falling water (and later oil) droplets. His study established that any particular droplet's electrical charge is a multiple of a definite, fundamental value—the electron's charge—and thus a confirmation that all electrons have the same charge and mass. Beginning in 1912, he spent several years investigating and finally proving Albert Einstein's proposed linear relationship between energy and frequency, and providing the first direct photoelectric support for the Planck constant. In 1923 Millikan was awarded the Nobel Prize for Physics.
+In 1909, S. P. L. Sørensen invented the pH concept and developed methods for measuring acidity. In 1911, Antonius Van den Broek proposed the idea that the elements on the periodic table are more properly organized by positive nuclear charge rather than atomic weight. In 1911, the first Solvay Conference was held in Brussels, bringing together most of the most prominent scientists of the day. In 1912, William Henry Bragg and William Lawrence Bragg proposed Bragg's law and established the field of X-ray crystallography, an important tool for elucidating the crystal structure of substances. In 1912, Peter Debye used the concept of a molecular dipole to describe asymmetric charge distribution in some molecules.
+
+=== Otto Hahn ===
+
+Otto Hahn was a German chemist and a pioneer in the fields of radioactivity and radiochemistry. He played a leading role in the discovery of nuclear fission and established nuclear chemistry as a scientific field. Hahn, Lise Meitner and Fritz Strassmann discovered radioactive isotopes of radium, thorium, protactinium and uranium. He also discovered the phenomena of atomic recoil and nuclear isomerism, and pioneered rubidium–strontium dating. In 1938, Hahn, Meitner and Strassmann discovered nuclear fission. In their second publication on nuclear fission in February 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of a nuclear chain reaction. Hahn received the 1944 Nobel Prize for Chemistry for the discoveries. Nuclear fission was the basis for nuclear reactors and nuclear weapons.
+
+=== Niels Bohr ===

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+
+In 1913, Niels Bohr, a Danish physicist, introduced the concepts of quantum mechanics to atomic structure by proposing what is now known as the Bohr model of the atom, where electrons exist only in strictly defined circular orbits around the nucleus similar to rungs on a ladder. The Bohr Model is a planetary model in which the negatively charged electrons orbit a small, positively charged nucleus similar to the planets orbiting the Sun (except that the orbits are not planar) – the gravitational force of the solar system is mathematically akin to the attractive Coulomb (electrical) force between the positively charged nucleus and the negatively charged electrons.
+In the Bohr model, however, electrons orbit the nucleus in orbits that have a set size and energy – the energy levels are said to be quantized, which means that only certain orbits with certain radii are allowed; orbits in between simply do not exist. The energy of the orbit is related to its size – that is, the lowest energy is found in the smallest orbit. Bohr also postulated that electromagnetic radiation is absorbed or emitted when an electron moves from one orbit to another. Because only certain electron orbits are permitted, the emission of light accompanying a jump of an electron from an excited energy state to ground state produces a unique emission spectrum for each element. Bohr later received the Nobel Prize in physics for this work.
+Niels Bohr also worked on the principle of complementarity, which states that an electron can be interpreted in two mutually exclusive and valid ways. Electrons can be interpreted as wave or particle models. His hypothesis was that an incoming particle would strike the nucleus and create an excited compound nucleus. This formed the basis of his liquid drop model and later provided a theory base for nuclear fission after its discovery by chemists Otto Hahn and Fritz Strassman, and explanation and naming by physicists Lise Meitner and Otto Frisch.
+
+In 1913, Henry Moseley, working from Van den Broek's earlier idea, introduced the concept of atomic number to fix some inadequacies of Mendeleev's periodic table, which had been based on atomic weight. The peak of Frederick Soddy's career in radiochemistry was in 1913 with his formulation of the concept of isotopes, which stated that certain elements exist in two or more forms which have different atomic weights but which are indistinguishable chemically. He is remembered for proving the existence of isotopes of certain radioactive elements, and is also credited, along with others, with the discovery of the element protactinium in 1917. In 1913, J. J. Thomson expanded on the work of Wien by showing that charged subatomic particles can be separated by their mass-to-charge ratio, a technique known as mass spectrometry.
+
+=== Gilbert N. Lewis ===
+
+American physical chemist Gilbert N. Lewis laid the foundation of valence bond theory; he was instrumental in developing a bonding theory based on the number of electrons in the outermost "valence" shell of the atom. In 1902, while Lewis was trying to explain valence to his students, he depicted atoms as constructed of a concentric series of cubes with electrons at each corner. This "cubic atom" explained the eight groups in the periodic table and represented his idea that chemical bonds are formed by electron transference to give each atom a complete set of eight outer electrons (an "octet").
+Lewis's theory of chemical bonding continued to evolve and, in 1916, he published his seminal article "The Atom of the Molecule", which suggested that a chemical bond is a pair of electrons shared by two atoms. Lewis's model equated the classical chemical bond with the sharing of a pair of electrons between the two bonded atoms. Lewis introduced the "electron dot diagrams" in this paper to symbolize the electronic structures of atoms and molecules. Now known as Lewis structures, they are discussed in virtually every introductory chemistry book.
+Shortly after the publication of his 1916 paper, Lewis became involved with military research. He did not return to the subject of chemical bonding until 1923, when he masterfully summarized his model in a short monograph entitled Valence and the Structure of Atoms and Molecules. His renewal of interest in this subject was largely stimulated by the activities of the American chemist and General Electric researcher Irving Langmuir, who between 1919 and 1921 popularized and elaborated Lewis's model. Langmuir subsequently introduced the term covalent bond. In 1921, Otto Stern and Walther Gerlach established the concept of quantum mechanical spin in subatomic particles.
+For cases where no sharing was involved, Lewis in 1923 developed the electron pair theory of acids and base: Lewis redefined an acid as any atom or molecule with an incomplete octet that was thus capable of accepting electrons from another atom; bases were, of course, electron donors. His theory is known as the concept of Lewis acids and bases. In 1923, G. N. Lewis and Merle Randall published Thermodynamics and the Free Energy of Chemical Substances, first modern treatise on chemical thermodynamics.
+The 1920s saw a rapid adoption and application of Lewis's model of the electron-pair bond in the fields of organic and coordination chemistry. In organic chemistry, this was primarily due to the efforts of the British chemists Arthur Lapworth, Robert Robinson, Thomas Lowry, and Christopher Ingold; while in coordination chemistry, Lewis's bonding model was promoted through the efforts of the American chemist Maurice Huggins and the British chemist Nevil Sidgwick.
+
+=== Quantum mechanics ===

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+
+In 1924, French quantum physicist Louis de Broglie published his thesis, in which he introduced a revolutionary theory of electron waves based on wave–particle duality. In his time, the wave and particle interpretations of light and matter were seen as being at odds with one another, but de Broglie suggested that these seemingly different characteristics were instead the same behavior observed from different perspectives—that particles can behave like waves, and waves (radiation) can behave like particles. Broglie's proposal offered an explanation of the restricted motion of electrons within the atom. The first publications of Broglie's idea of "matter waves" had drawn little attention from other physicists, but a copy of his doctoral thesis chanced to reach Einstein, whose response was enthusiastic. Einstein stressed the importance of Broglie's work both explicitly and by building further on it.
+In 1925, Austrian-born physicist Wolfgang Pauli developed the Pauli exclusion principle, which states that no two electrons around a single nucleus in an atom can occupy the same quantum state simultaneously, as described by four quantum numbers. Pauli made major contributions to quantum mechanics and quantum field theory – he was awarded the 1945 Nobel Prize for Physics for his discovery of the Pauli exclusion principle – as well as solid-state physics, and he successfully hypothesized the existence of the neutrino. In addition to his original work, he wrote masterful syntheses of several areas of physical theory that are considered classics of scientific literature.
+
+In 1926 at the age of 39, Austrian theoretical physicist Erwin Schrödinger produced the papers that gave the foundations of quantum wave mechanics. In those papers he described his partial differential equation that is the basic equation of quantum mechanics and bears the same relation to the mechanics of the atom as Newton's equations of motion bear to planetary astronomy. Adopting a proposal made by Louis de Broglie in 1924 that particles of matter have a dual nature and in some situations act like waves, Schrödinger introduced a theory describing the behaviour of such a system by a wave equation that is now known as the Schrödinger equation. The solutions to Schrödinger's equation, unlike the solutions to Newton's equations, are wave functions that can only be related to the probable occurrence of physical events. The readily visualized sequence of events of the planetary orbits of Newton is, in quantum mechanics, replaced by the more abstract notion of probability. (This aspect of the quantum theory made Schrödinger and several other physicists profoundly unhappy, and he devoted much of his later life to formulating philosophical objections to the generally accepted interpretation of the theory that he had done so much to create.)
+German theoretical physicist Werner Heisenberg was one of the key creators of quantum mechanics. In 1925, Heisenberg discovered a way to formulate quantum mechanics in terms of matrices. For that discovery, he was awarded the Nobel Prize for Physics for 1932. In 1927 he published his uncertainty principle, upon which he built his philosophy and for which he is best known. Heisenberg was able to demonstrate that if you were studying an electron in an atom you could say where it was (the electron's location) or where it was going (the electron's velocity), but it was impossible to express both at the same time. He also made important contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles, and he was instrumental in planning the first West German nuclear reactor at Karlsruhe, together with a research reactor in Munich, in 1957. Considerable controversy surrounds his work on atomic research during World War II.
+
+=== Quantum chemistry ===
+
+Some view the birth of quantum chemistry in the discovery of the Schrödinger equation and its application to the hydrogen atom in 1926. However, the 1927 article of Walter Heitler and Fritz London is often recognised as the first milestone in the history of quantum chemistry. This is the first application of quantum mechanics to the diatomic hydrogen molecule, and thus to the phenomenon of the chemical bond. In the following years much progress was accomplished by Edward Teller, Robert S. Mulliken, Max Born, J. Robert Oppenheimer, Linus Pauling, Erich Hückel, Douglas Hartree and Vladimir Aleksandrovich Fock, to cite a few.
+Still, skepticism remained as to the general power of quantum mechanics applied to complex chemical systems. The situation around 1930 is described by Paul Dirac:
+
+The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation.

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+
+Hence the quantum mechanical methods developed in the 1930s and 1940s are often referred to as theoretical molecular or atomic physics to underline the fact that they were more the application of quantum mechanics to chemistry and spectroscopy than answers to chemically relevant questions. In 1951, a milestone article in quantum chemistry is the seminal paper of Clemens C. J. Roothaan on Roothaan equations. It opened the avenue to the solution of the self-consistent field equations for small molecules like hydrogen or nitrogen. Those computations were performed with the help of tables of integrals which were computed on the most advanced computers of the time.
+In the 1940s many physicists turned from molecular or atomic physics to nuclear physics (like J. Robert Oppenheimer or Edward Teller). Glenn T. Seaborg was an American nuclear chemist best known for his work on isolating and identifying transuranium elements (those heavier than uranium). He shared the 1951 Nobel Prize for Chemistry with Edwin Mattison McMillan for their independent discoveries of transuranium elements. Seaborgium was named in his honour, making him the only person, along with Albert Einstein and Yuri Oganessian, for whom a chemical element was named during his lifetime.
+
+=== Molecular biology and biochemistry ===
+
+By the mid 20th century, in principle, the integration of physics and chemistry was extensive, with chemical properties explained as the result of the electronic structure of the atom; Linus Pauling's book on The Nature of the Chemical Bond used the principles of quantum mechanics to deduce bond angles in ever-more complicated molecules. However, though some principles deduced from quantum mechanics were able to predict qualitatively some chemical features for biologically relevant molecules, they were, till the end of the 20th century, more a collection of rules, observations, and recipes than rigorous ab initio quantitative methods. 
+
+This heuristic approach triumphed in 1953 when James Watson and Francis Crick deduced the double helical structure of DNA by constructing models constrained by and informed by the knowledge of the chemistry of the constituent parts and the X-ray diffraction patterns obtained by Rosalind Franklin. This discovery lead to an explosion of research into the biochemistry of life.
+In the same year, the Miller–Urey experiment demonstrated that basic constituents of protein, simple amino acids, could themselves be built up from simpler molecules in a simulation of primordial processes on Earth. This first attempt by chemists to study hypothetical processes in the laboratory under controlled conditions helped kickstart bountiful research, within the natural sciences, into the origins of life.
+In 1983 Kary Mullis devised a method for the in-vitro amplification of DNA, known as the polymerase chain reaction (PCR), which revolutionized the chemical processes used in the laboratory to manipulate it. PCR could be used to synthesize specific pieces of DNA and made possible the sequencing of DNA of organisms, which culminated in the Human Genome Project.
+An important piece in the double helix puzzle was solved by one of Pauling's students Matthew Meselson and Frank Stahl, the result of their collaboration (Meselson–Stahl experiment) has been called as "the most beautiful experiment in biology".
+They used a centrifugation technique that sorted molecules according to differences in weight. Because nitrogen atoms are a component of DNA, they were labelled and therefore tracked in replication in bacteria.
+
+=== Late 20th century ===
+
+In 1970, John Pople developed the Gaussian program greatly easing computational chemistry calculations. In 1971, Yves Chauvin offered an explanation of the reaction mechanism of olefin metathesis reactions. In 1975, Karl Barry Sharpless and his group discovered stereoselective oxidation reactions including Sharpless epoxidation, Sharpless asymmetric dihydroxylation, and Sharpless oxyamination.
+In 1985, Harold Kroto, Robert Curl and Richard Smalley discovered fullerenes, a class of large carbon molecules superficially resembling the geodesic dome designed by architect R. Buckminster Fuller. In 1991, Sumio Iijima used electron microscopy to discover a type of cylindrical fullerene known as a carbon nanotube, though earlier work had been done in the field as early as 1951. This material is an important component in the field of nanotechnology. In 1994, K. C. Nicolaou with his group  and Robert A. Holton and his group, achieved the first total synthesis of Taxol. In 1995, Eric Cornell and Carl Wieman produced the first Bose–Einstein condensate, a substance that displays quantum mechanical properties on the macroscopic scale.
+
+== Mathematics and chemistry ==
+Before the 20th century, chemistry was defined as the science of the nature of matter and its transformations. It was therefore distinct from physics which was not concerned with such dramatic transformation of matter. Moreover, in contrast to physics, chemistry remained predominantly a descriptive and empirical science until the end of the 19th century. Though they developed a consistent quantitative foundation based on notions of atomic and molecular weights, combining proportions, and thermodynamic quantities, chemists had less use of advanced mathematics. Some even expressed reluctance about the use of mathematics within chemistry. For example, the philosopher Auguste Comte wrote in 1830:
+
+Every attempt to employ mathematical methods in the study of chemical questions must be considered profoundly irrational and contrary to the spirit of chemistry.... if mathematical analysis should ever hold a prominent place in chemistry – an aberration which is happily almost impossible – it would occasion a rapid and widespread degeneration of that science.
+However, in the second part of the 19th century, the situation began to change as August Kekulé wrote in 1867:
+
+I rather expect that we shall someday find a mathematico-mechanical explanation for what we now call atoms which will render an account of their properties.
+
+== Scope of chemistry ==
+As understanding of the nature of matter has evolved, so too has the self-understanding of the science of chemistry by its practitioners. This continuing historical process of evaluation includes the categories, terms, aims and scope of chemistry. Additionally, the development of the social institutions and networks which support chemical enquiry are highly significant factors that enable the production, dissemination and application of chemical knowledge. (See Philosophy of chemistry)
+
+=== Chemical industry ===

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+
+The later part of the nineteenth century saw a huge increase in the exploitation of petroleum extracted from the earth for the production of a host of chemicals and largely replaced the use of whale oil, coal tar and naval stores used previously. Large-scale production and refinement of petroleum provided feedstocks for liquid fuels such as gasoline and diesel, solvents, lubricants, asphalt, waxes, and for the production of many of the common materials of the modern world, such as synthetic fibers, plastics, paints, detergents, pharmaceuticals, adhesives and ammonia as fertilizer and for other uses. Many of these required new catalysts and the utilization of chemical engineering for their cost-effective production.
+In the mid-twentieth century, control of the electronic structure of semiconductor materials was made precise by the creation of large ingots of extremely pure single crystals of silicon and germanium. Accurate control of their chemical composition by doping with other elements made the production of the solid state transistor in 1951 and made possible the production of tiny integrated circuits for use in electronic devices, especially computers.
+
+== See also ==
+
+=== Histories and timelines ===
+
+=== Notable chemists ===
+listed chronologically:
+
+== Notes ==
+
+== References ==
+Selected classic papers from the history of chemistry
+Biographies of Chemists Archived 2017-07-08 at the Wayback Machine
+CHEM-HIST: International Mailing List for the History of Chemistry
+Eric R. Scerri, The Periodic Table: Its Story and Its Significance, Oxford University Press, 2006.
+
+== Further reading ==
+Ana Maria Alfonso-Goldfarb et al., eds (2015). Crossing Oceans: Exchange of Products, Instruments, Procedures and Ideas in the History of Chemistry and Related Sciences, Coleção CLE/UNICAMP, volume 75.
+Morris, Peter J. T.; Rocke, Alan, eds. (2022). A Cultural History of Chemistry. Volumes 1–6. London: Bloomsbury. ISBN 9781474294928.
+Beretta, Marco, ed. (2022). A Cultural History Of Chemistry in Antiquity (Volume 1). London: Bloomsbury. doi:10.5040/9781474203746. ISBN 978-1-4742-9453-9.
+Jensen, William B (2006). "Textbooks and the future of the history of chemistry as an academic discipline". Bulletin for the History of Chemistry. 3: 1–8. doi:10.70359/bhc2006v031p001.
+Multhauf, Robert P. (1966). The Origins of Chemistry. London: Oldbourne. OCLC 977570829.
+Partington, James R. (1961–1964). A History of Chemistry. London: Macmillan. OCLC 1149250811. (four volumes)
+Principe, Lawrence M. (2013). The Secrets of Alchemy. Chicago: University of Chicago Press. ISBN 978-0226103792. (general overview of the history of alchemy and chemistry, with a focus on the relationship between the two; written in a highly accessible style)
+Rampling, Jennifer M (2017). "The Future of the History of Chemistry". Ambix. 64 (4): 295–300. doi:10.1080/00026980.2017.1434970. PMID 29448901.
+Rampling, Jennifer M. (2020). The Experimental Fire: Inventing English Alchemy, 1300-1700. Chicago: University of Chicago Press. ISBN 9780226826547.
+Documentaries
+BBC (2010). Chemistry: A Volatile History.
+
+== External links ==
+
+ChemisLab – Chemists of the Past
+SHAC: Society for the History of Alchemy and Chemistry

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+Alchemy is defined by the Hermetic quest for the philosopher's stone, the study of which is steeped in symbolic mysticism, and differs greatly from modern science. Alchemists toiled to make transformations on an esoteric (spiritual) and/or exoteric (practical) level. It was the protoscientific, exoteric aspects of alchemy that contributed heavily to the evolution of chemistry in Greco-Roman Egypt, in the Islamic Golden Age, and then in Europe. Alchemy and chemistry share an interest in the composition and properties of matter, and until the 18th century they were not separate disciplines. The term chymistry has been used to describe the blend of alchemy and chemistry that existed before that time.
+During the Renaissance, exoteric alchemy remained popular in the form of Paracelsian iatrochemistry, while spiritual alchemy flourished, realigned to its Platonic, Hermetic, and Gnostic roots. Consequently, the symbolic quest for the philosopher's stone was not superseded by scientific advances, and was still the domain of respected scientists and doctors until the early 18th century. Early modern alchemists who are renowned for their scientific contributions include Jan Baptist van Helmont, Robert Boyle, and Isaac Newton.
+
+=== Alchemy in the Islamic world ===
+
+In the Islamic World, the Muslims were translating the works of ancient Greek and Hellenistic philosophers into Arabic and were experimenting with scientific ideas. The Arabic works attributed to the 8th-century alchemist Jābir ibn Hayyān introduced a systematic classification of chemical substances, and provided instructions for deriving an inorganic compound (sal ammoniac or ammonium chloride) from organic substances (such as plants, blood, and hair) by chemical means. Some Arabic Jabirian works (e.g., the "Book of Mercy", and the "Book of Seventy") were later translated into Latin under the Latinized name "Geber", and in 13th-century Europe an anonymous writer, usually referred to as pseudo-Geber, started to produce alchemical and metallurgical writings under this name. Influential scholars, such as Abū al-Rayhān al-Bīrūnī and Avicenna disputed the theories of alchemy, particularly the theory of the transmutation of metals.
+During the period of Islamic Alchemy, works attributed to Geber correctly identified sulfur and mercury as elements.
+
+=== Problems encountered with alchemy ===
+There were several problems with alchemy, as seen from today's standpoint. There was no systematic naming scheme for new compounds, and the language was esoteric and vague to the point that the terminologies meant different things to different people. In fact, according to The Fontana History of Chemistry (Brock, 1992):
+
+The language of alchemy soon developed an arcane and secretive technical vocabulary designed to conceal information from the uninitiated. To a large degree, this language is incomprehensible to us today, though it is apparent that readers of Geoffrey Chaucer's Canon's Yeoman's Tale or audiences of Ben Jonson's The Alchemist were able to construe it sufficiently to laugh at it.
+
+Chaucer's tale exposed the more fraudulent side of alchemy, especially the manufacture of counterfeit gold from cheap substances. Less than a century earlier, Dante Alighieri also demonstrated an awareness of this fraudulence, causing him to consign all alchemists to the Inferno in his writings. Soon afterwards, in 1317, the Avignon Pope John XXII ordered all alchemists to leave France for making counterfeit money. A law was passed in England in 1403 which made the "multiplication of metals" punishable by death. Despite these and other apparently extreme measures, alchemy did not die. Royalty and privileged classes still sought to discover the philosopher's stone and the elixir of life for themselves.
+There was also no agreed-upon scientific method for making experiments reproducible. Indeed, many alchemists included in their methods irrelevant information such as the timing of the tides or the phases of the moon. The esoteric nature and codified vocabulary of alchemy appeared to be more useful in concealing the fact that they could not be sure of very much at all. As early as the 14th century, cracks seemed to grow in the facade of alchemy; and people became sceptical. Clearly, there needed to be a scientific method in which experiments could be repeated by other people, and results needed to be reported in a clear language that laid out both what was known and what was unknown.
+
+== 17th and 18th centuries: Early chemistry ==

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+Practical attempts to improve the refining of ores and their extraction to smelt metals was an important source of information for early chemists in the 16th century, among them Georg Agricola (1494–1555), who published his great work De re metallica in 1556. His work describes the highly developed and complex processes of mining metal ores, metal extraction and metallurgy of the time. His approach removed the mysticism associated with the subject, creating the practical base upon which others could build. The work describes the many kinds of furnace used to smelt ore, and stimulated interest in minerals and their composition. It is no coincidence that he gives numerous references to the earlier author, Pliny the Elder and his Naturalis Historia. Agricola has been described as the "father of metallurgy" and the founder of geology as a scientific discipline.
+In 1605, Sir Francis Bacon published The Proficience and Advancement of Learning, which contains a description of what would later be known as the scientific method. In 1605, Michal Sedziwój publishes the alchemical treatise A New Light of Alchemy which proposed the existence of the "food of life" within air, much later recognized as oxygen. In 1615 Jean Beguin published the Tyrocinium Chymicum, an early chemistry textbook, and in it draws the first-ever chemical equation. In 1637 René Descartes publishes Discours de la méthode, which contains an outline of the scientific method.
+The Dutch chemist Jan Baptist van Helmont's work Ortus medicinae was published posthumously in 1648; the book is cited by some as a major transitional work between alchemy and chemistry, and as an important influence on Robert Boyle. The book contains the results of numerous experiments and establishes an early version of the law of conservation of mass. Working during the time just after Paracelsus and iatrochemistry, Jan Baptist van Helmont suggested that there are insubstantial substances other than air and coined a name for them – "gas", from the Greek word chaos. In addition to introducing the word "gas" into the vocabulary of scientists, van Helmont conducted several experiments involving gases. Jan Baptist van Helmont is also remembered today largely for his ideas on spontaneous generation and his 5-year tree experiment, as well as being considered the founder of pneumatic chemistry.
+
+=== Robert Boyle ===
+
+The Anglo-Irish chemist Robert Boyle (1627–1691) is considered to have initiated the gradual separation of chemistry from alchemy. Although skeptical of elements and convinced of alchemy, Boyle played a key part in elevating the "sacred art" as an independent, fundamental and philosophical discipline. He is best known for Boyle's law, which he presented in 1662, though he was not the first to discover it. The law describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system.
+Boyle is also credited for his landmark publication The Sceptical Chymist (1661), which advocated for a rigorous approach to experimentation among chemists. In the work, Boyle questioned some commonly held alchemical theories and argued for practitioners to be more "philosophical" and less commercially focused. He rejected the classical four elements of earth, fire, air, and water, and proposed a mechanistic alternative of atoms and chemical reactions that could be subject to rigorous experiment.
+Boyle also tried to purify chemicals to obtain reproducible reactions. He was a vocal proponent of the mechanical philosophy proposed by René Descartes to explain and quantify the physical properties and interactions of material substances. Boyle was an atomist, but favoured the word corpuscle over atoms. He commented that the finest division of matter where the properties are retained is at the level of corpuscles.
+Boyle repeated the tree experiment of van Helmont, and was the first to use indicators which changed colors with acidity. He also performed numerous investigations with an air pump, and noted that the mercury fell as air was pumped out. He also observed that pumping the air out of a container would extinguish a flame and kill small animals placed inside. Through his works, Boyle helped to lay the foundations for the chemical revolution two centuries later.
+
+=== Development and dismantling of phlogiston ===

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+In 1702, German chemist Georg Stahl coined the name "phlogiston" for the substance believed to be released in the process of burning. Around 1735, Swedish chemist Georg Brandt analyzed a dark blue pigment found in copper ore. Brandt demonstrated that the pigment contained a new element, later named cobalt. In 1751, a Swedish chemist and pupil of Stahl's named Axel Fredrik Cronstedt, identified an impurity in copper ore as a separate metallic element, which he named nickel. Cronstedt is one of the founders of modern mineralogy. Cronstedt also discovered the mineral scheelite in 1751, which he named tungsten, meaning "heavy stone" in Swedish.
+In 1754, Scottish chemist Joseph Black isolated carbon dioxide, which he called "fixed air". In 1757, Louis Claude Cadet de Gassicourt, while investigating arsenic compounds, creates Cadet's fuming liquid, later discovered to be cacodyl oxide, considered to be the first synthetic organometallic compound. In 1758, Joseph Black formulated the concept of latent heat to explain the thermochemistry of phase changes. In 1766, English chemist Henry Cavendish isolated hydrogen, which he called "inflammable air". Cavendish discovered hydrogen as a colorless, odourless gas that burns and can form an explosive mixture with air, and published a paper on the production of water by burning inflammable air (that is, hydrogen) in dephlogisticated air (now known to be oxygen), the latter a constituent of atmospheric air (phlogiston theory).
+In 1773, Swedish German chemist Carl Wilhelm Scheele discovered oxygen, which he called "fire air", but did not immediately publish his achievement. In 1774, English chemist Joseph Priestley independently isolated oxygen in its gaseous state, calling it "dephlogisticated air", and published his work before Scheele. During his lifetime, Priestley's considerable scientific reputation rested on his invention of soda water, his writings on electricity, and his discovery of several "airs" (gases), the most famous being what Priestley dubbed "dephlogisticated air" (oxygen). However, Priestley's determination to defend phlogiston theory and to reject what would become the chemical revolution eventually left him isolated within the scientific community.
+In 1781, Carl Wilhelm Scheele discovered that a new acid, tungstic acid, could be made from Cronstedt's scheelite (at the time named tungsten). Scheele and Torbern Bergman suggested that it might be possible to obtain a new metal by reducing this acid. In 1783, José and Fausto Elhuyar found an acid made from wolframite that was identical to tungstic acid. Later that year, in Spain, the brothers succeeded in isolating the metal now known as tungsten by reduction of this acid with charcoal, and they are credited with the discovery of the element.
+
+=== Volta and the Voltaic pile ===
+
+Italian physicist Alessandro Volta constructed a device for accumulating a large charge by a series of inductions and groundings. He investigated the 1780s discovery "animal electricity" by Luigi Galvani, and found that the electric current was generated from the contact of dissimilar metals, and that the frog leg was only acting as a detector. Volta demonstrated in 1794 that when two metals and brine-soaked cloth or cardboard are arranged in a circuit they produce an electric current.
+In 1800, Volta stacked several pairs of alternating copper (or silver) and zinc discs (electrodes) separated by cloth or cardboard soaked in brine (electrolyte) to increase the electrolyte conductivity. When the top and bottom contacts were connected by a wire, an electric current flowed through this voltaic pile and the connecting wire. Thus, Volta is credited with constructing the first electrical battery to produce electricity.
+Thus, Volta is considered to be the founder of the discipline of electrochemistry. A Galvanic cell (or voltaic cell) is an electrochemical cell that derives electrical energy from a spontaneous redox reaction taking place within the cell. It generally consists of two different metals connected by a salt bridge, or individual half-cells separated by a porous membrane.
+
+=== Antoine-Laurent de Lavoisier ===
+
+Antoine-Laurent de Lavoisier demonstrated with careful measurements that transmutation of water to earth was not possible, but that the sediment observed from boiling water came from the container. He burnt phosphorus and sulfur in air, and proved that the products weighed more than the original samples, with the mass gained being lost from the air. Thus, in 1789, he established the Law of Conservation of Mass, which is also called "Lavoisier's Law."

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+Repeating the experiments of Priestley, he demonstrated that air is composed of two parts, one of which combines with metals to form calxes. In Considérations Générales sur la Nature des Acides (1778), he demonstrated that the "air" responsible for combustion was also the source of acidity. The next year, he named this portion oxygen (Greek for acid-former), and the other azote (Greek for no life). Because of his more thorough characterization of it as an element, Lavoisier thus has a claim to the discovery of oxygen along with Priestley and Scheele. He also discovered that the "inflammable air" discovered by Cavendish – which he termed hydrogen (Greek for water-former) – combined with oxygen to produce a dew, as Priestley had reported, which appeared to be water. In Reflexions sur le Phlogistique (1783), Lavoisier showed the phlogiston theory of combustion to be inconsistent. Mikhail Lomonosov independently established a tradition of chemistry in Russia in the 18th century; he also rejected the phlogiston theory, and anticipated the kinetic theory of gases. Lomonosov regarded heat as a form of motion, and stated the idea of conservation of matter.
+Lavoisier worked with Claude Louis Berthollet and others to devise a system of chemical nomenclature, which serves as the basis of the modern system of naming chemical compounds. In his Methods of Chemical Nomenclature (1787), Lavoisier invented the system of naming and classification still largely in use today, including names such as sulfuric acid, sulfates, and sulfites. In 1785, Berthollet was the first to introduce the use of chlorine gas as a commercial bleach. In the same year he first determined the elemental composition of the gas ammonia. Berthollet first produced a modern bleaching liquid in 1789 by passing chlorine gas through a solution of sodium carbonate – the result was a weak solution of sodium hypochlorite. Another strong chlorine oxidant and bleach which he investigated and was the first to produce, potassium chlorate (KClO3), is known as Berthollet's Salt. Berthollet is also known for his scientific contributions to the theory of chemical equilibrium via the mechanism of reversible reactions.
+
+Lavoisier's Traité Élémentaire de Chimie (Elementary Treatise of Chemistry, 1789) was the first modern chemical textbook, and presented a unified view of new theories of chemistry, contained a clear statement of the Law of Conservation of Mass, and denied the existence of phlogiston. In addition, it contained a list of elements, or substances that could not be broken down further, which included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, and sulfur. His list, however, also included light and caloric, which he believed to be material substances. In the work, Lavoisier underscored the observational basis of his chemistry, stating "I have tried...to arrive at the truth by linking up facts; to suppress as much as possible the use of reasoning, which is often an unreliable instrument which deceives us, in order to follow as much as possible the torch of observation and of experiment." Nevertheless, he believed that the real existence of atoms was philosophically impossible. Lavoisier demonstrated that organisms disassemble and reconstitute atmospheric air in the same manner as a burning body.
+With Pierre-Simon Laplace, Lavoisier used a calorimeter to estimate the heat evolved per unit of carbon dioxide produced. They found the same ratio for a flame and animals, indicating that animals produced energy by a type of combustion. Lavoisier believed in the radical theory, which stated that radicals, which function as a single group in a chemical reaction, would combine with oxygen in reactions. He believed all acids contained oxygen. He also discovered that diamond is a crystalline form of carbon.
+Although many of Lavoisier's partners were influential for the advancement of chemistry as a scientific discipline, his wife Marie-Anne Lavoisier was arguably the most influential of them all. Upon their marriage, Mme. Lavoisier began to study chemistry, English, and drawing in order to help her husband in his work either by translating papers into English, a language which Lavoisier did not know, or by keeping records and drawing the various apparatuses that Lavoisier used in his labs. Through her ability to read and translate articles from Britain for her husband, Lavoisier had access to knowledge of many of the chemical advances happening outside of his lab. Furthermore, Mme. Lavoisier kept records of her husband's work and ensured that his works were published. The first sign of Marie-Anne's true potential as a chemist in Lavoisier's lab came when she was translating a book by the scientist Richard Kirwan. While translating, she stumbled upon and corrected multiple errors. When she presented her translation, along with her notes, to Lavoisier, her contributions led to Lavoisier's refutation of the theory of phlogiston.
+Lavoisier made many fundamental contributions to the science of chemistry. Following his work, chemistry acquired a strict, quantitative nature, allowing reliable predictions to be made. The revolution in chemistry which he brought about was a result of a conscious effort to fit all experiments into the framework of a single theory. He established the consistent use of chemical balance, used oxygen to overthrow the phlogiston theory, and developed a new system of chemical nomenclature. Further potential contributions were cut short when Lavoisier was beheaded during the French Revolution.

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+---
+title: "History of chemistry"
+chunk: 7/20
+source: "https://en.wikipedia.org/wiki/History_of_chemistry"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:38.639255+00:00"
+instance: "kb-cron"
+---
+
+== 19th century ==
+Throughout the 19th century, chemistry was divided between those who followed the atomic theory of John Dalton and the energeticists, such as Wilhelm Ostwald and Ernst Mach. Although such proponents of the atomic theory as Amedeo Avogadro and Ludwig Boltzmann made great advances in explaining the behavior of gases, this dispute was not finally settled until Jean Perrin's experimental investigation of Einstein's atomic explanation of Brownian motion in the first decade of the 20th century.
+Well before the dispute had been settled, many had already applied the concept of atomism to chemistry. A major example was the ion theory of Svante Arrhenius which anticipated ideas about atomic substructure that did not fully develop until the 20th century. Michael Faraday was another early worker, whose major contribution to chemistry was electrochemistry, in which (among other things) a certain quantity of electricity during electrolysis or electrodeposition of metals was shown to be associated with certain quantities of chemical elements, and fixed quantities of the elements therefore with each other, in specific ratios. These findings, like those of Dalton's combining ratios, were early clues to the atomic nature of matter.
+
+=== John Dalton ===
+
+In 1803, English meteorologist and chemist John Dalton proposed Dalton's law, which describes the relationship between the components in a mixture of gases and the relative pressure each contributes to that of the overall mixture. Discovered in 1801, this concept is also known as Dalton's law of partial pressures.
+Dalton also proposed a modern atomic theory in 1803 which stated that all matter was composed of small indivisible particles termed atoms, atoms of a given element possess unique characteristics and weight, and three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules). In 1808, Dalton first published New System of Chemical Philosophy (1808–1827), in which he outlined the first modern scientific description of the atomic theory. This work identified chemical elements as a specific type of atom, therefore rejecting Newton's theory of chemical affinities.
+Instead, Dalton inferred proportions of elements in compounds by taking ratios of the weights of reactants, setting the atomic weight of hydrogen to be identically one. Following Jeremias Benjamin Richter (known for introducing the term stoichiometry), he proposed that chemical elements combine in integral ratios. This is known as the law of multiple proportions or Dalton's law, and Dalton included a clear description of the law in his New System of Chemical Philosophy. The law of multiple proportions is one of the basic laws of stoichiometry used to establish the atomic theory. Despite the importance of the work as the first view of atoms as physically real entities and the introduction of a system of chemical symbols, New System of Chemical Philosophy devoted almost as much space to the caloric theory as to atomism.
+French chemist Joseph Proust proposed the law of definite proportions, which states that elements always combine in small, whole number ratios to form compounds, based on several experiments conducted between 1797 and 1804. Along with the law of multiple proportions, the law of definite proportions forms the basis of stoichiometry. The law of definite proportions and constant composition do not prove that atoms exist, but they are difficult to explain without assuming that chemical compounds are formed when atoms combine in constant proportions.
+
+=== Jöns Jacob Berzelius ===
+
+A Swedish chemist and disciple of Dalton, Jöns Jacob Berzelius embarked on a systematic program to try to make accurate and precise quantitative measurements and to ensure the purity of chemicals. Along with Lavoisier, Boyle, and Dalton, Berzelius is known as the father of modern chemistry. In 1828 he compiled a table of relative atomic weights, where oxygen was used as a standard, with its weight set at 100, and which included all of the elements known at the time. This work provided evidence in favor of Dalton's atomic theory – that inorganic chemical compounds are composed of atoms combined in whole number amounts. He determined the exact elementary constituents of a large number of compounds; the results strongly supported Proust's Law of Definite Proportions. In discovering that atomic weights are not integer multiples of the weight of hydrogen, Berzelius also disproved Prout's hypothesis that elements are built up from atoms of hydrogen.
+Motivated by his extensive atomic weight determinations and in a desire to aid his experiments, he introduced the classical system of chemical symbols and notation with his 1808 publication Lärbok i Kemien, in which elements are abbreviated to one or two letters to make a distinct symbol from their Latin name. This system of chemical notation—in which the elements were given simple written labels, such as O for oxygen, or Fe for iron, with proportions denoted by numbers—is the same basic system used today. The only difference is that instead of the subscript number used today (e.g., H2O), Berzelius used a superscript (H2O). Berzelius is credited with identifying the chemical elements silicon, selenium, thorium, and cerium. Students working in Berzelius's laboratory also discovered lithium and vanadium.
+Berzelius developed the radical theory of chemical combination, which holds that reactions occur as stable groups of atoms called radicals are exchanged between molecules. He believed that salts are compounds formed of acids and bases, and discovered that the anions in acids were attracted to a positive electrode (the anode), whereas the cations in a base were attracted to a negative electrode (the cathode). Berzelius did not believe in the Vitalism Theory, but instead in a regulative force which produced organization of tissues in an organism. Berzelius is also credited with originating the chemical terms "catalysis", "polymer", "isomer", and "allotrope", although his original definitions differ dramatically from modern usage. For example, he coined the term "polymer" in 1833 to describe organic compounds which shared identical empirical formulas but which differed in overall molecular weight, the larger of the compounds being described as "polymers" of the smallest. By this long-superseded, pre-structural definition, glucose (C6H12O6) was viewed as a polymer of formaldehyde (CH2O).

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+title: "History of chemistry"
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+date_saved: "2026-05-05T03:10:38.639255+00:00"
+instance: "kb-cron"
+---
+
+=== New elements and gas laws ===
+
+English chemist Humphry Davy was a pioneer in the field of electrolysis, using Alessandro Volta's voltaic pile to split up common compounds and thus isolate a series of new elements. He went on to electrolyse molten salts and discovered several new metals, especially sodium and potassium, highly reactive elements known as the alkali metals. Potassium, the first metal that was isolated by electrolysis, was discovered in 1807 by Davy, who derived it from caustic potash (KOH). Before the 19th century, no distinction was made between potassium and sodium. Sodium was first isolated by Davy in the same year by passing an electric current through molten sodium hydroxide (NaOH). When Davy heard that Berzelius and Pontin prepared calcium amalgam by electrolyzing lime in mercury, he tried it himself. Davy was successful, and discovered calcium in 1808 by electrolyzing a mixture of lime and mercuric oxide. He worked with electrolysis throughout his life and, in 1808, he isolated magnesium, strontium and barium.
+Davy also experimented with gases by inhaling them. This experimental procedure nearly proved fatal on several occasions, but led to the discovery of the unusual effects of nitrous oxide, which came to be known as laughing gas. Chlorine was discovered in 1774 by Swedish chemist Carl Wilhelm Scheele, who called it "dephlogisticated marine acid" (see phlogiston theory) and mistakenly thought it contained oxygen. Scheele observed several properties of chlorine gas, such as its bleaching effect on litmus, its deadly effect on insects, its yellow-green colour, and the similarity of its smell to that of aqua regia. However, Scheele was unable to publish his findings at the time. In 1810, chlorine was given its current name by Humphry Davy (derived from the Greek word for green), who insisted that chlorine was in fact an element. He also showed that oxygen could not be obtained from the substance known as oxymuriatic acid (HCl solution). This discovery overturned Lavoisier's definition of acids as compounds of oxygen. Davy was a popular lecturer and able experimenter.
+
+French chemist Joseph Louis Gay-Lussac shared the interest of Lavoisier and others in the quantitative study of the properties of gases. From his first major program of research in 1801–1802, he concluded that equal volumes of all gases expand equally with the same increase in temperature: this conclusion is usually called "Charles's law", as Gay-Lussac gave credit to Jacques Charles, who had arrived at nearly the same conclusion in the 1780s but had not published it. The law was independently discovered by British natural philosopher John Dalton by 1801, although Dalton's description was less thorough than Gay-Lussac's. In 1804 Gay-Lussac made several daring ascents of over 7,000 meters above sea level in hydrogen-filled balloons—a feat not equaled for another 50 years—that allowed him to investigate other aspects of gases. Not only did he gather magnetic measurements at various altitudes, but he also took pressure, temperature, and humidity measurements and samples of air, which he later analyzed chemically.
+In 1808 Gay-Lussac announced what was probably his single greatest achievement: from his own and others' experiments he deduced that gases at constant temperature and pressure combine in simple numerical proportions by volume, and the resulting product or products—if gases—also bear a simple proportion by volume to the volumes of the reactants. In other words, gases under equal conditions of temperature and pressure react with one another in volume ratios of small whole numbers. This conclusion subsequently became known as "Gay-Lussac's law" or the "Law of Combining Volumes". With his fellow professor at the École Polytechnique, Louis Jacques Thénard, Gay-Lussac also participated in early electrochemical research, investigating the elements discovered by its means. Among other achievements, they decomposed boric acid by using fused potassium, thus discovering the element boron. The two also took part in contemporary debates that modified Lavoisier's definition of acids and furthered his program of analyzing organic compounds for their oxygen and hydrogen content.
+The element iodine was discovered by French chemist Bernard Courtois in 1811. Courtois gave samples to his friends, Charles Bernard Desormes (1777–1862) and Nicolas Clément (1779–1841), to continue research. He also gave some of the substance to Gay-Lussac and to physicist André-Marie Ampère. On December 6, 1813, Gay-Lussac announced that the new substance was either an element or a compound of oxygen. It was Gay-Lussac who suggested the name "iode", from the Greek word ιώδες (iodes) for violet (because of the color of iodine vapor). Ampère had given some of his sample to Humphry Davy. Davy did some experiments on the substance and noted its similarity to chlorine. Davy sent a letter dated December 10 to the Royal Society of London stating that he had identified a new element. Arguments erupted between Davy and Gay-Lussac over who identified iodine first, but both scientists acknowledged Courtois as the first to isolate the element.
+In 1815, Humphry Davy invented the Davy lamp, which allowed miners within coal mines to work safely in the presence of flammable gases. There had been many mining explosions caused by firedamp or methane often ignited by open flames of the lamps then used by miners. Davy conceived of using an iron gauze to enclose a lamp's flame, and so prevent the methane burning inside the lamp from passing out to the general atmosphere. Although the idea of the safety lamp had already been demonstrated by William Reid Clanny and by the then unknown (but later very famous) engineer George Stephenson, Davy's use of wire gauze to prevent the spread of flame was used by many other inventors in their later designs. There was some discussion as to whether Davy had discovered the principles behind his lamp without the help of the work of Smithson Tennant, but it was generally agreed that the work of both men had been independent. Davy refused to patent the lamp, and its invention led to him being awarded the Rumford medal in 1816.

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+title: "History of chemistry"
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+category: "reference"
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+date_saved: "2026-05-05T03:10:38.639255+00:00"
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+---
+
+After Dalton published his atomic theory in 1808, certain of his central ideas were soon adopted by most chemists. However, uncertainty persisted for half a century about how atomic theory was to be configured and applied to concrete situations; chemists in different countries developed several different incompatible atomistic systems. A paper that suggested a way out of this difficult situation was published as early as 1811 by the Italian physicist Amedeo Avogadro (1776–1856), who hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules, from which it followed that relative molecular weights of any two gases are the same as the ratio of the densities of the two gases under the same conditions of temperature and pressure. Avogadro also reasoned that simple gases were not formed of solitary atoms but were instead compound molecules of two or more atoms. Thus Avogadro was able to overcome the difficulty that Dalton and others had encountered when Gay-Lussac reported that above 100 °C the volume of water vapor was twice the volume of the oxygen used to form it. According to Avogadro, the molecule of oxygen had split into two atoms in the course of forming water vapor.
+Avogadro's hypothesis was neglected for half a century after it was first published. Many reasons for this neglect have been cited, including some theoretical problems, such as Jöns Jacob Berzelius's "dualism", which asserted that compounds are held together by the attraction of positive and negative electrical charges, making it inconceivable that a molecule composed of two electrically similar atoms—as in oxygen—could exist. An additional barrier to acceptance was the fact that many chemists were reluctant to adopt physical methods (such as vapour-density determinations) to solve their problems. By mid-century, however, some leading figures had begun to view the chaotic multiplicity of competing systems of atomic weights and molecular formulas as intolerable. Moreover, purely chemical evidence began to mount that suggested Avogadro's approach might be right after all. During the 1850s, younger chemists, such as Alexander Williamson in England, Charles Gerhardt and Charles-Adolphe Wurtz in France, and August Kekulé in Germany, began to advocate reforming theoretical chemistry to make it consistent with Avogadrian theory.
+
+=== Wöhler, von Liebig, organic chemistry and the vitalism debate ===
+
+In 1825, Friedrich Wöhler and Justus von Liebig performed the first confirmed discovery and explanation of isomers, earlier named by Berzelius. Working with cyanic acid and fulminic acid, they correctly deduced that isomerism was caused by differing arrangements of atoms within a molecular structure. In 1827, William Prout classified biomolecules into their modern groupings: carbohydrates, proteins and lipids. After the nature of combustion was settled, a dispute about vitalism and the essential distinction between organic and inorganic substances began. The vitalism question was revolutionized in 1828 when Friedrich Wöhler synthesized urea, thereby establishing that organic compounds could be produced from inorganic starting materials and disproving the theory of vitalism.
+This opened a new research field in chemistry, and by the end of the 19th century, scientists were able to synthesize hundreds of organic compounds. The most important among them are mauve, magenta, and other synthetic dyes, as well as the widely used drug aspirin. The discovery of the artificial synthesis of urea contributed greatly to the theory of isomerism, as the empirical chemical formulas for urea and ammonium cyanate are identical (see Wöhler synthesis). In 1832, Friedrich Wöhler and Justus von Liebig discovered and explained functional groups and radicals in relation to organic chemistry, as well as first synthesizing benzaldehyde. Liebig, a German chemist, made major contributions to agricultural and biological chemistry, and worked on the organization of organic chemistry, being considered one of its principal founders. Liebig is also considered the "father of the fertilizer industry" for his discovery of nitrogen as an essential plant nutrient, and his formulation of the Law of the Minimum which described the effect of individual nutrients on crops.
+
+=== Vladimir Markovnikov ===
+
+Vladimir Markovnikov, born in 1838, was a Russian scientist who did most of his work at Kazan University in Russia. At Kazan, he studied under Butlerov in a laboratory better known as "the cradle of Russian organic chemistry", after which he also studied chemistry in Germany for two years. Markovnikov's contributions to the fields of organic chemistry included the development of the eponymous Markovnikov's rule, which states that hydrogen halides when added to alkenes and alkynes would add in a way that hydrogens would bond to the side of the carbon with the most hydrogen substituents. Products in chemistry that follow this rule are considered Markovnikov products and those that did not are considered anti-Markovnikov products. Markovnikov's rule was an early example of regioselectivity in organic synthesis and the modern understanding of it continues to be important in the chemical industry, where catalysts have been developed to produce anti-Markovnikov products. A significant aspect of Markovnikov's rule is that it explains reactivity based on the structural arrangement of atoms, as many chemists at the time did not consider chemical formulas as representing physical arrangement of atoms (see also radical theory).

data/en.wikipedia.org/wiki/History_of_chemistry-9.md

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+---
+title: "History of chemistry"
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+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:38.639255+00:00"
+instance: "kb-cron"
+---
+
+=== Mid-1800s ===
+In 1840, Germain Hess proposed Hess's law, an early statement of the law of conservation of energy, which establishes that energy changes in a chemical process depend only on the states of the starting and product materials and not on the specific pathway taken between the two states. In 1847, Hermann Kolbe obtained acetic acid from completely inorganic sources, further disproving vitalism. In 1848, William Thomson, 1st Baron Kelvin (commonly known as Lord Kelvin) established the concept of absolute zero, the temperature at which all molecular motion ceases. In 1849, Louis Pasteur discovered that the racemic form of tartaric acid is a mixture of the levorotatory and dextrotatory forms, thus clarifying the nature of optical rotation and advancing the field of stereochemistry. In 1852, August Beer proposed Beer's law, which explains the relationship between the composition of a mixture and the amount of light it will absorb. Based partly on earlier work by Pierre Bouguer and Johann Heinrich Lambert, it established the analytical technique known as spectrophotometry. In 1855, Benjamin Silliman, Jr. pioneered methods of petroleum cracking, which made the entire modern petrochemical industry possible.
+
+Avogadro's hypothesis began to gain broad appeal among chemists only after his compatriot and fellow scientist Stanislao Cannizzaro demonstrated its value in 1858, two years after Avogadro's death. Cannizzaro's chemical interests had originally centered on natural products and on reactions of aromatic compounds; in 1853 he discovered that when benzaldehyde is treated with concentrated base, both benzoic acid and benzyl alcohol are produced—a phenomenon known today as the Cannizzaro reaction. In his 1858 pamphlet, Cannizzaro showed that a complete return to the ideas of Avogadro could be used to construct a consistent and robust theoretical structure that fit nearly all of the available empirical evidence. For instance, he pointed to evidence that suggested that not all elementary gases consist of two atoms per molecule—some were monatomic, most were diatomic, and a few were even more complex.
+Another point of contention had been the formulas for compounds of the alkali metals (such as sodium) and the alkaline earth metals (such as calcium), which, in view of their striking chemical analogies, most chemists had wanted to assign to the same formula type. Cannizzaro argued that placing these metals in different categories had the beneficial result of eliminating certain anomalies when using their physical properties to deduce atomic weights. Unfortunately, Cannizzaro's pamphlet was published initially only in Italian and had little immediate impact. The real breakthrough came with an international chemical congress held in the German town of Karlsruhe in September 1860, at which most of the leading European chemists were present. The Karlsruhe Congress had been arranged by Kekulé, Wurtz, and a few others who shared Cannizzaro's sense of the direction chemistry should go. Speaking in French (as everyone there did), Cannizzaro's eloquence and logic made an indelible impression on the assembled body. Moreover, his friend Angelo Pavesi distributed Cannizzaro's pamphlet to attendees at the end of the meeting; more than one chemist later wrote of the decisive impression the reading of this document provided. For instance, Lothar Meyer later wrote that on reading Cannizzaro's paper, "The scales seemed to fall from my eyes." Cannizzaro thus played a crucial role in winning the battle for reform. The system advocated by him, and soon thereafter adopted by most leading chemists, is substantially identical to what is still used today.
+
+=== Perkin, Crookes, and Nobel ===
+In 1856, Sir William Henry Perkin, age 18, given a challenge by his professor, August Wilhelm von Hofmann, sought to synthesize quinine, the anti-malaria drug, from coal tar. In one attempt, Perkin oxidized aniline using potassium dichromate, whose toluidine impurities reacted with the aniline and yielded a black solid—suggesting a "failed" organic synthesis. Cleaning the flask with alcohol, Perkin noticed purple portions of the solution: a byproduct of the attempt was the first synthetic dye, known as mauveine or Perkin's mauve. Perkin's discovery is the foundation of the dye synthesis industry, one of the earliest successful chemical industries.
+German chemist August Kekulé von Stradonitz's most important single contribution was his structural theory of organic composition, outlined in two articles published in 1857 and 1858 and treated in great detail in the pages of his extraordinarily popular Lehrbuch der organischen Chemie ("Textbook of Organic Chemistry"), the first installment of which appeared in 1859 and gradually extended to four volumes. Kekulé argued that tetravalent carbon atoms – that is, carbon forming exactly four chemical bonds – could link together to form what he called a "carbon chain" or a "carbon skeleton," to which other atoms with other valences (such as hydrogen, oxygen, nitrogen, and chlorine) could join. He was convinced that it was possible for the chemist to specify this detailed molecular architecture for at least the simpler organic compounds known in his day. Kekulé was not the only chemist to make such claims in this era. The Scottish chemist Archibald Scott Couper published a substantially similar theory nearly simultaneously, and the Russian chemist Aleksandr Butlerov did much to clarify and expand structure theory. However, it was predominantly Kekulé's ideas that prevailed in the chemical community.

data/en.wikipedia.org/wiki/List_of_chemical_elements_named_after_people-0.md

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+---
+title: "List of chemical elements named after people"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/List_of_chemical_elements_named_after_people"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T03:10:37.286553+00:00"
+instance: "kb-cron"
+---
+
+This list of chemical elements named after people includes elements named for people both directly and indirectly. Of the 118 elements, 19 are connected with the names of 20 people. 15 elements were named to honor 16 scientists (as curium honours both Marie and Pierre Curie). Four others have indirect connection to the names of non-scientists. Only gadolinium and samarium occur in nature; the rest are man-made.
+
+
+== List ==
+These 19 elements are connected to the names of people. Seaborg and Oganessian were the only living persons honored by having elements named after them; Oganessian is the only one still alive. Names were proposed to honor Einstein and Fermi while they were still alive, but they had both died by the time those names became official.
+The four elements associated with non-scientists were not named in their honor but named for something else bearing their name: samarium for the mineral samarskite from which it was isolated; and americium, berkelium and livermorium after places named for them. The cities of Berkeley, California and Livermore, California are the locations of the University of California Radiation Laboratory and Lawrence Livermore National Laboratory, respectively.
+Six elements have only an indirect namesake: samarium, gadolinium, americium, berkelium, flerovium, and livermorium were each named for a mineral or place that were themselves named for people.
+
+
+== Other connections ==
+Other element names connected with people (real or mythological) have been proposed but failed to gain official international recognition. The following such names received past significant use among scientists:
+
+cassiopeium after the constellation Cassiopeia, hence indirectly connected to the mythological Cassiopeia (now lutetium);
+columbium after Christopher Columbus (now niobium);
+hahnium after Otto Hahn (now dubnium, also later proposed for what is now hassium);
+joliotium after Irène Joliot-Curie (now nobelium, also later proposed for what is now dubnium);
+kurchatovium after Igor Kurchatov (now rutherfordium);
+Names had also been suggested (but not used) to honour Henri Becquerel (becquerelium) and Paul Langevin (langevinium). George Gamow, Lev Landau, and Vitalii Goldanski (who was alive at the time) were suggested for consideration for honoring with elements during the Transfermium Wars, but were not actually proposed.
+(See the article on element naming controversies and List of chemical elements named after places.)
+Also, mythological entities have had a significant impact on the naming of elements. Helium, titanium, selenium, palladium, promethium, cerium, europium, tantalum, mercury, thorium, uranium, neptunium and plutonium are all given names connected to mythological characters. With some, that connection is indirect:
+
+helium: named for the Sun where it was discovered by spectral analysis, being associated with the deity Helios,
+iridium: named for the Greek goddess Iris,
+tellurium: named for the Roman goddess of the earth, Tellus Mater,
+niobium: named for Niobe, a character of Greek mythology,
+vanadium: named for Vanadis, another name for Norse goddess Freyja,
+selenium: named for the Moon being associated with the deity Selene,
+palladium: named for the then-recently discovered asteroid Pallas which had been named for the deity Pallas Athena,
+cerium: named for the then-recently discovered asteroid Ceres which had been named for the deity Ceres,
+europium: named for the continent that had been named after Europa.
+Titanium is unique in that it refers to a group of deities rather than any particular individual. So Helios, Selene, Pallas, and Prometheus actually have two elements named in their honor.
+And for elements given a name connected with a group, there is also xenon, named for the Greek word ξένον (xenon), neuter singular form of ξένος (xenos), meaning 'foreign(er)', 'strange(r)', or 'guest'.
+Its discoverer William Ramsay intended this name to be an indication of the qualities of this element in analogy to the generic group of people.
+Gallium was discovered by French scientist Paul-Émile Lecoq de Boisbaudran, who named it in honor of France ("Gallia" in Latin); allegations were later made that he had also named it for himself, as "gallus" is Latin for "le coq", but he denied that this had been his intention.
+
+
+== See also ==
+List of scientists whose names are used as units
+List of scientists whose names are used in physical constants
+List of chemical elements named after places
+List of chemical element name etymologies
+Naming of chemical elements
+List of chemical elements
+
+
+== References ==