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Chemistry

CHEMISTRY.

Where and when did chemistry originate? Some chemists would identify ancient Egypt as the birthplace of chemistry because of that culture's glassworks, cosmetics, and mummification techniques. Advocates of this theory might also refer to a possible etymology of the word chemistry from the Egyptian word for black. Other historians place the origins of chemistry amid ancient Greek theories of matter that formulated the basic conceptsprinciples, elements, and atomsfor understanding the individuality of material substances and their transformations. Others would argue that chemistry emerged in medieval alchemy: alchemists invented the laboratory that is still the site for the production of chemical knowledge, and they established and transmitted techniques and instruments that are still at work in many chemical processes. Meanwhile, historians of institutional life would assert that chemistry emerged in seventeenth-century Europe when public lectures and chairs of chemistry were created.

The variety of answers to the question of origins points to the multiple identities of chemistry. A posteriori it seems natural to consider chemistry as an autonomous academic science with technological applications in a variety of domains. However, this is only one face of chemistry. Whether we consider chemistry as a set of technological practicessuch as metal reduction, dyeing, glass-makingor as a theory of matter transformations, or as a teachable and public knowledge enjoying an academic status, the chronological marks change dramatically.

The question of origin cannot be settled not only because chemistry is multifaceted, but also because the answer depends heavily on the image of chemistry one wants to convey. For instance, eighteenth-century chemists strongly denied any connection between chemistry and alchemy. The kind of useful and reliable discipline they wanted to promote on the academic stage was contrasted with the obscurity and fraudulent practices of alchemists, although this is a discontinuity seriously questioned by historians of alchemy at the turn of the twenty-first century.

Alchemy in the Scientific Revolution

First, historians of alchemy note that there was no linguistic distinction between chemistry and alchemy in the seventeenth centuryboth disciplines being named "chymistry." Second, against the popular view of alchemy as a spiritual quest based on religious symbolism, historians such as Lawrence Principe and William Newman claim that "chymists" did actually manipulate and transform matter. While the religious interpretation of alchemy served to distance it from chemistry, they emphasize the continuity and argue that medieval alchemists already had developed experimental methods often considered as chief characteristics of modern science. They established a number of tests to identify substances; they used analysis and synthesis in order to demonstrate the similarity between substances extracted from nature and substances artificially produced in the laboratory; and they used weight measurements and the balance-sheet method traditionally credited to Antoine-Laurent de Lavoisier (17431794) to determine the identity of substances.

Early modern "chymistry" also questions the grand narrative of the scientific revolution, with Galileo Galilei's (15641642) and Robert Boyle's (16271691) mechanical philosophy whisking away the alchemical tradition. Boyle's view of material phenomena as being produced by the interaction of small particles that have only primary qualities (size, shape, and motion) by no means implied a rejection of the alchemical tradition. Since Jabir ibn Hayyan (c. 721c. 851), whose work was spread and discussed in the West in the thirteenth century, the discipline of alchemy had fostered a corpuscular view of matter that was later developed by Daniel Sennert (15721657), an early seventeenth-century chemist. Sennert managed to reconfigure the Aristotelian theory of matter by combining the four principles with Democritean atomism. In order to provide experimental demonstration that matter at the microlevel is made by the juxtaposition of atoms, he performed a reductio in pristinum statum (reduction into the pristine state). Although Boyle positioned himself as a "natural philosopher" against "chymical philosophers, he was in debt to Sennert, since he tacitly used his experiments and his theoretical framework in his early essays as well as in The Sceptical Chymist (1680).

In addition, Boyle's skepticism did not apply to alchemical transmutations. Until his death, he kept seeking the philosopher's stone, using the knowledge he had learned in his youth from the American chymist George Starkey (16271665), who also initiated Sir Isaac Newton (16421727). Boyle, the advocate of public knowledge at the Royal Society, concealed his transmutational processes in secret language.

Thus, two of the celebrated founding fathers of modern science, Boyle and Newton, were dedicated believers in alchemical transmutation. Since Betty Dobbs's 1975 work, The Foundations of Newton's Alchemy: or, "The Hunting of the Greene Lyon," historians of chemistry have reconsidered the impact of Newton's bold chemical hypothesis at the end of his Opticks (1704). In the famous Query 31, Newton ventured an interpretation of chemical reactions in terms of attraction between the smallest particles of matter. A uniform attractive force allowed the smallest particles to cohere and form aggregates whose "virtue" gradually decreased as the aggregates became bigger and bigger. Whereas this hypothesis has been read as an extrapolation of gravitational physics to chemistry, it is possible to view it as a way to rationalize chemical practices that was impossible in Cartesian mechanism. Newton allowed chemists to understand and measure affinities in purely chemical terms.

Eighteenth-Century Cultures of Chemistry

Such was the program initiated by Etienne-François Geoffroy (Geoffroy the Elder; 16721731), who published a "Table des rapports" (table of affinities) in 1718. The substance at the head of a column is followed by all the substances that could combine with it in order of decreasing affinitythe degree of affinity being indicated by the place in the column. A substance C that displaces B from a combination AB to form AC will be located above B in the column because of its stronger affinity for A. Displacement reactions thus provided a qualitative measure of affinities and allowed predicting the outcome of reactions. Thus, chemistry came to be seen as a predictive and useful science in the eighteenth century.

It is important to stress that long before Lavoisier, chemistry had conquered the status of an autonomous academic discipline. A chemistry class had been established at the Paris Academy of Science in the late seventeenth century, whereas the physics class was only created in 1785. The chemistry class conducted systematic research programs in plant analysis and mineralogy. Not only were chemistry chairs established in a number of European universities, but also innumerable public and private courses of chemistry opened up with experimental demonstrations. They were attended by a variety of audiences: pharmacists, metallurgists, as well as gentlemen and "philosophes" who practiced chemistry as enlightened amateurs. Chemistry was promoted alongside Enlightenment values as a rational and useful knowledge that would be of benefit to economy and society. A key strategy for winning political support was the introduction of the distinction between "pure" and "applied" chemistry by Johan Gottschalk Wallerius (17091785), who took the chair of chemistry in Uppsala in 1753. This distinction asserted the dignity of pure chemistry while transforming the chronological priority of chemical arts into a logical dependence upon "pure" knowledge. Chemistry could thus be perceived as a legitimate academic discipline in university curricula and highly valued for its usefulness in various applications. At the same time in France, chemistry was celebrated in the context of the Encyclopédie as a model science based on empirical data rather than on a priori speculations, a science requiring craft and labor, cultivated by skilled "artists" working hard in their laboratories unlike those lazy philosophers who never took off the academic gown.

However, chemistry was more than a fashionable science. So decisive was the success of Lavoisier's revolution in the 1780s that most chemists and historians of science, according to Frederic Holmes, "viewed eighteenth-century chemistry as the stage on which the drama of the chemical revolution was performed" (Holmes, 1989, p. 3). They once described it as an obscure and inconsistent set of practical rules based on the erroneous phlogiston theory. This theory, shaped by Georg-Ernst Stahl in the early eighteenth century, explained a number of phenomena such as combustion, as well as properties such as metals or acids, by the action of an invisible principle or fire named phlogistan (from the Greek term for "burnt"). The canonical story thus culminated in Lavoisier's questioning the existence of phlogiston and its alleged presence in metals, in acids, in combustion and respiration, and consequently overthrowing the old paradigm.

When historians resist the temptation to read eighteenth-century chemistry backward, waiting for Lavoisier to arrive on the stage, they quickly realize that this standard picture was only one aspect among numerous diverse cultures of chemistry in the eighteenth century, many of which were extremely innovative. In workshops and firms, the invention of continuous processes led to what historians of industry described as "the chemical revolution." In more academic spaces, laboratory practices were also deeply changed by the study of salt solutions when wet analysis was added to the traditional fire analysis and color indicators were systematically applied to acids and alkalis. This change, especially visible in the research program conducted at the Paris Academy of Science on plant and mineral analysis, had a theoretical impact: chemists gave up the old concept of salt as a universal principle, in favor of the notion of middle salta substance resulting from the combination of volatile and nonvolatile salts or of alkali and acid. This redefinition subverted the traditional notion of principles as material entities as bearers of properties. Substances could present similar properties and belong to the same class despite their different constituent principles. The idea of interchangeability was reinforced by the displacement reactions that allowed the construction of affinity tables. Affinity tables favored the view that the behavior of a "mixt" (compound) depends less upon the nature of its constituent principles than on its relations with other substances. The relational identity of chemical substances minimized the importance of principleswhether they be three, four, or fivethat chemists used to oppose to the mechanistic view of a "catholic matter." Moreover in a number of eighteenth-century chemistry coursesfor instance in Hermann Boerhaave's (16681738) textbook and Guillaume-François Rouelle's (17031770) lectureselements were often redefined as "agents" of chemical reactions rather than as constituent principles. Elements were consequently presented as "natural instruments" together with "artificial instruments" such as laboratory vessels, furnaces, and alembics. This pragmatic notion of elements accompanied their redefinition in operational terms as substances that could not be further decomposed by available analytic techniques.

From Phlogiston to Oxygen

In addition, the phlogiston theory was neither an overarching nor a rigid framework. The notion, which was first forged by Georg Ernst Stahl (c. 16601734) around 1700, was most often mixed either with Newton's views of matter that inspired salt and affinity chemistry or with various notions inspired by local mining or pharmaceutical traditions. It is therefore difficult to identify a unitary phlogiston theory that would define eighteenth-century chemistry. Rather, two distinct phlogiston theories prevailed in two different contexts. In mid-eighteenth-century France, Stahl was considered as the founder of chemistry when Rouelle and his pupils redefined Stahl's "inflammable earth" as fire. The fire principle, always invisible because it circulated from one combination to another one, imparted combustibility or metallic properties when it was "fixed." It was released during combustion and metals calcination. Indeed, there was a difficulty here: if phlogiston was released when metals calcinated, how would one explain their increase of weight? The anomaly had been known for decades and had not prevented the success of this powerful theoretical framework since, as Immanuel Kant and Lavoisier himself acknowledged, it was Stahl's merit to realize that combustion and reduction were two inverse reactions and that calcination and combustion were one and the same process despite their phenomenological dissimilarities. Lavoisier cast doubts on phlogiston when he addressed the question of weight increase in 1772. After conducting experiments of combustion of phosphorus and lead calcination with careful weighing of each ingredient and each piece of apparatus before and after the reaction took place, he concluded that the weight gain could be due to a combination with part of the air contained under the flask. Although Lavoisier was convinced that his discovery was about to cause a revolutionary change in physics and chemistry, he could not yet refute that combustion released phlogiston. Unsurprisingly many contemporary chemists adopted a compromise between the two interpretations, and Pierre-Joseph Macquer (17181784) redefined phlogiston as the principle of light distinct from heat. Meanwhile an "English phlogiston" emerged from pneumatic studies that gained a sound phenomenological reality through its assimilation with hydrogen.

The study of gases so much changed the landscape of chemistry in the 1770s that some contemporary chemists used the phrase "the pneumatic revolution." Although air had been considered as one of the four elements, it was considered as a mechanical agent rather than as a chemical reactant until Stephen Hales (16771761), a British plant physiologist, built a "pneumatic chest" for collecting gases released by physiological processes. With this apparatus chemists were able to collect the gases given off by chemical reactions, to measure their volume, and to submit them to various tests. Joseph Black (17281799) identified "fixed air" (carbon dioxide) in 1756; in 1766, Henry Cavendish (17311810) isolated "inflammable air" (hydrogen); in 1772 Joseph Priestley (17331804) described a dozen new airs in his Experiments and Observations on Different Kinds of Air. In 1774 Karl Wilhelm Scheele (17421786), a Swedish pharmacist, isolated and described a new air that made a candle flame brighter and facilitated respiration. By the same time, Priestley had also produced a similar air by the reduction of the "red precipitate of mercury," a result that he communicated to Lavoisier when he visited him in Paris in October 1774.

Lavoisier was a latecomer in the crowd of chemists "hunting" airs, his earlier interest in chemistry being related to geology. His attention was drawn to the mechanisms of fixation and release of gases when he discovered the role of air in combustion. He consequently became aware of the British workswith the help of his wife Marie-Anne-Pierrette Paulze-Lavoisier (17581836), who translated foreign publications for him. He conducted systematic experiments on "elastic fluids" that were published in his Opusucles physiques et chymiques in 1774. He repeated Priestley's reduction of the red precipitate of mercury and performed the reverse operation of calcining mercury. Whereas Priestley characterized the gas released as "deplogisticated air" Lavoisier concluded in 1778 that this gas was "the purest part of the air."

Two alternative views of gases were in competition. For the British pneumatists, the various gases isolated were composed of one single air differentiated according to the proportion of phlogiston they contained. In other terms, they fit nicely into the phlogiston paradigm. They even reinforced it because a pneumatic science, whose unquestioned leader was Priestly and which allowed a better understanding of physiological processes in plants and animals as well as medical applications, emerged. By contrast, Lavoisier came to see atmospheric air as a compound and developed a theory of gaseous state. All solid or liquid substances could be in a gaseous state depending on the quantity of caloric (or heat) they fix. Thanks to his caloric theory of gases, Lavoisier was in a better position to refute the phlogiston theory of combustion. He could account for the release of heat once he admitted that combustion consisted in a combination with a portion of atmospheric air that released its caloric. This portion of air that he first named "vital air"later renamed oxygenwould play a key role in Lavoisier's chemistry. Not only did it explain combustion and calcinations but it was also the principle of acidity. Therefore, during the controversy that followed, Lavoisier's theory was referred to as "oxygen theory" or sometimes "antiphlogistic theory." Phlogiston was condemned as a useless chimerical entity, only to be replaced by another enigmatic principle of heat, "caloric," while the omnipresent element oxygen's being a bearer of properties was an echo of the older chemistry.

Revolution or Foundation?

Lavoisier's revolution did not condemn the old notion of elements common to all substances, although he destroyed three of the traditional four elements, fire, air, and water. The demonstration that water was not an element but a compound of two gases was made in a solemn experiment of analysis and synthesis of water set up in February 1785. It required heavy and expensive equipment designed with the help of a military engineer and with the support of an academic Commission of Study for the Improvement of Balloons. With this spectacular experiment Lavoisier won his first allies. Together they were able to take advantage of the opportunity to reform the chemical language as outlined by Louis Bernard Guyton de Morveau (17371816) and build up a new "Method of Chymical Nomenclature" that reflected Lavoisier's theory and eliminated phlogiston. The new system, published in 1777, was seen as a coup d'état and sparkled a fierce controversy. The anti-phlogisticians mobilized all resources, including the creation of a new journal, Annales de chimie, in order to convince European chemists. Moreover, to defeat the last and attractive British version of phlogiston as inflammable air (hydrogen), which was articulated by Richard Kirwan (17321812), Madame Lavoisier translated into French his Essai sur le phlogistique (1788; Essay on phlogiston), while the anti-phlogisticians criticized the author's view in footnotes. Beyond the issue of phlogiston, numerous objections to the new language were raised by contemporary chemists concerning the choice of terms, such as "oxygen" (an acid generator according to Lavoisier's theory of acids) and "azote" (improper for animal life and a property of many other gases). Although the French "nomenclators" did not change any term, their system was finally adopted throughout Europe by 1800. But this victory did not always mean conversion to all facets of Lavoisier's chemistry. The reform of language fulfilled a long-felt need among the chemical community and it came at the right moment: textbooks were needed to train pharmacists as well as chemists for burgeoning industries. The new systematic language and Lavoisier's Elements of Chemistry (1789) facilitated the teaching of chemistry.

In the context of the French Revolution, which resulted in Lavoisier's death on the guillotine and the creation of a new educational system, Lavoisier's revolution has been perceived as the destruction of premodern chemistry and the foundation of modern chemistry on a tabula rasa. However, the celebration of the founding hero overemphasizes the impact of his contribution to chemistry. Lavoisier did not overthrow the whole of chemistry. The tradition of salt and affinity chemistry remained untouched. Rather, the latter was revised and integrated in a grandiose "Newtonian dream" by Claude-Louis Berthollet (17481822) in his Essai de statique chimique (1803). Lavoisier invented neither the "law of conservation of matter"a kind of axiomatic principle tacitly assumed by all natural scientists long before himnor the laws of chemical proportions that inspired the chemical atomism developed by the next generation of chemists.

Nineteenth-Century Chemical Atoms

Nineteenth-century chemistry has often been described as a smooth sequence of discoveries that gradually established modern chemistry. Positivist historians were content with reporting landmark events such as John Dalton's atomic theory, Amedeo Avogadro's law, Dmitry Ivanovich Mendeleev's periodic system, and so on. In thus conveying a cumulative process, they not only distorted history but also tended to deprive past scientists of inner consistency because they failed to accept many of these "great discoveries."

One major feature of nineteenth-century chemistry is that the history of ideas did not follow the pathway that seems logical from a present-day perspective. For instance, the laws of chemical proportions did not follow from Lavoisier's program. Instead, they emerged from salt chemistry, more precisely from attempts to determine the weight or ponderous quantity of a base that could neutralize a definite quantity of acid. While the chemical revolution was drawing all attention toward Paris, two German chemists, Karl Friedrich Wenzel (17401793) and Jeremias Richter (17621807), were initiating a quantitative chemistry that they named stöichiometrie or stoichiometry (from the Greek stoicheion, or element). The main assumption that the properties of any substance depend upon the nature and proportion of its constituent elements opened up a research program for chemists whose key words were analysis and quantification (titration or dosage).

The field of stoichiometry was extended in 1802 when Joseph Louis Proust (17541826) applied Richter's notion of "equivalent," so far limited to reactions between acids and bases, to all combinations and formulated a general law: the relationships of the masses according to which two or several elements combine are fixed and not susceptible of continuous variations. While Berthollet questioned the generality of Proust's law of definite proportions, John Dalton (17661844), a professor at Manchester, made it the basis for his atomic hypothesis. He assumed that chemical combinations take place unit by unit, or atom by atom. He added a law of multiple proportions: when two elements form more than one compound, the weight proportions of the element that combines with a fixed proportion of another one are in a simple numerical ratio. Dalton's hypothesis rested on the assumption that atoms were solid and indivisible, that they were surrounded by an atmosphere of heat, that there were as many kinds of atoms as there were elements. Dalton's atoms were not the uniform and minute discrete units that structured all material bodies of ancient atomism. Rather, they were minimum and discrete units of chemical combination. And Dalton assumed that atoms would combine in the simplest way, that is, two atoms formed a binary compound. The main advantage of Dalton's hypothesis was that it allowed simple formulas. Instead of determining the composition of a body by percentages, chemists could express it in terms of constituent atoms thanks to the determination of atomic weights. Of course it was impossible to weigh individual atoms. Since Dalton could not determine this weight by using the neutrality of the compound like Richter, he elected a conventional standard. He chose hydrogen as the unit of reference. For instance, hydrogen and oxygen were known to form water, whose analysis gave the ratio 87.4 parts by weight of oxygen for 12.6 of hydrogen. If hydrogen has a weight equal to 1, the relative atomic weight of an atom of oxygen will be roughly 7. Shortly after Dalton's New System of Chemical Philosophy (1808), Joseph Gay-Lussac (17781850) announced that volumes of gas that combine with each other were in direct proportion and that the volume of the compound thus formed was also in direct proportion with the volume of the constituent gases. The volumetric proportions thus seemed to confirm Dalton's weight ratios.

To explain the convergence, both Amedeo Avogadro (17761856) in 1811 and André-Marie Ampère (17751836) in 1814 suggested that in the same conditions of temperature and pressure, equal volumes of gases contain the same number of molecules. In order to admit this simple hypothesis, however, both men had to admit a second hypothesis: that when two gases joined to form a compound, the integrating molecules should divide into two parts.

From a modern perspective this hypothesis was a big step forward because it suggested the distinction between atoms and molecules. Why, then, was it rejected in the 1830s and for several decades afterward by the most prominent chemists? The rejection of Avogadro's law is a classical topos for illustrating the opposition between presentist and historicist approaches. The alleged "blindness" of nineteenth-century chemists appears as a perfectly consistent attitude once one considers that Avogadro's hypothesis of molecules formed of two atoms of the same element stood in contradiction to the theoretical framework of chemical atomism. In Dalton's theory, such diatomic molecules were physically impossible because of the repulsion between the atmospheres of heat of two identical atoms, and they were theoretically impossible in the new electrochemical paradigm set up by Jöns Jacob Berzelius (17791848) on the basis of his experiments on electrolytic decomposition. Elements were defined by their electric polarity, and the intensity of the positive or negative charge determined the affinity between them. Molecules of two atoms of the same element were impossible because of the repulsion between two identical electrical charges.

The distinction between atom and molecule did not directly follow from Avogadro's law. Rather it was formulated by a young chemist, Auguste Laurent (18071853), trained in mineralogy and crystallography. He challenged Berzelius's electrochemical view. For Berzelius all compounds resulted from the electric attraction between two elements. This dualistic view was extended to organic compounds thanks to the notion of radicalfor instance the benzoyl radical discovered by Leibiga group of atoms that, like elements, persisted through reactions. In the 1830s Jean-Baptiste-André Dumas (18001884) prepared trichloracetic acid by the substitution of three atoms of chlorine to three atoms of hydrogen in acetic acid. His student Laurent noticed the similarity of properties between the two acids. Electronegative atoms of chlorine could replace electropositive atoms of hydrogen without changing the properties too much. He consequently developed a unitary theory that Dumas called "type theory" in 1838: in organic compounds there exist types that persist when elements are changed. This suggested that the properties of compounds depended more on the architecture of molecules than on the nature of constituent atoms. Type theory applied to the increasing crowd of organic compounds while inorganic chemistry was still ruled by dualism.

Charles Frédéric Gerhardt (18161856) attempted to re-unify chemistry by extending the type theory to all compounds, using analogy as a guide. Although he admitted that we do not know anything about the actual arrangement of atoms in a molecule, he defined three typeshydrogen, water, and ammoniaas an ideal taxonomic scheme. According to Gerhardt, all compounds derived from these three types.

The theory of type implicitly indicated that atoms of different elements had different combining powers or valences. Hydrogen, for example, has a valence of one, while oxygen has two and nitrogen three. It is worth emphasizing that although nineteenth-century organic chemists such as Gerhardt and August Kekulé (18291896) did not believe in the actual existence of atoms and molecules, they were able to invent structural formulas that allowed them to predict and create new compounds.

The Construction of the Periodic System

Gerhardt's unitary perspective also provided the foundation for the construction of the periodic system. Dmitry Ivanovich Mendeleev (18341907) was certainly not the first chemist who tried to classify elements on the basis of atomic weights. Van Spronsen reasonably argued that the periodic system was codiscovered by six chemists in the 1860s. However, Mendeleev adopted a different strategy. He pointed to the Karlsruhe Conference, held in 1860, as the first step toward the periodic law. This first international meeting of chemists adopted atomic weights based on Avogadro's and Gerhardt's views. From the general agreement on the distinction between atoms and molecules, Mendeleev derived another crucial distinction, between simple body and element. Since Lavoisier's famous definition of elements as nondecomposed bodies, most chemists did not distinguish between the two terms. Mendeleev, on the contrary, stressed the difference between the simple substances, empirical residues of decomposition characterized by their physical properties and molecular weights, and the abstract element defined as an invisible ingredient and characterized by its atomic weight. Mendeleev chose to classify elements rather than simple bodies because he considered them as responsible for the properties of simple and compound substances. Mendeleev was thus the first chemist who really worried about a clear definition of what was to be classified. Although abstract and unobservable, Mendeleev's elements were material entities and true individuals. Mendeleev was a staunch opponent of the hypothesis formulated by William Prout (17851850), which asserted that the multitude of simple substances derived from one single primary element, usually identified as hydrogen. Throughout the nineteenth century this reductionist mainstream stimulated attempts at classifying elements. Classifications were mainly aimed at tracing genealogical relations or families by grouping analogous elements in triads or families according to the numerical ratios of their atomic weights. Starting from the assumption that elements would never be divided or transmuted into one another, Mendeleev took an opposite direction. He sought unity in a natural law ruling the multiple elements, rather than in matter itself. He compared the most dissimilar elements and firmly relied on the order of increasing atomic weights. Whereas grouping elements on the basis of valences always faced the difficulty of multiple valences, Mendeleev strictly relied on the order of increasing atomic weight, which he regarded as the constant criterion of the individuality of chemical elements.

Indeed, this criterion revealed some deficiencies. It sometimes blurred strong chemical analogies (for instance between Li and Mg, Be and Al, B and Si) or induced unexpected proximities (for example, in Mendeleev's eighth group). Mendeleev struggled with these difficulties and published thirty different tables in order to better suit his system with chemical analogies. However, his abstract notion of elements allowed predictions of unknown elements. Many of these elements were confirmed during Mendeleev's lifetime and served to validate his system while guarding it from further challenges. The discovery of a dozen rare earth elements in the late nineteenth century created difficulties because they lack individual properties and have strong mutual analogies. The inert gases were not welcomed either, first, because they had not been predicted, but mainly because they did not exhibit chemical properties. The atomic weights determined by William Ramsay (18521916) and Lord Rayleigh (John William Strutt; 18421919) for helium (4) and argon (40) would result in the placement of the latter between potassium and calcium according to its atomic weight. This was impossible, and the whole periodic system was in danger to collapse. Mendeleev raised doubts about the elemental nature of argon. Thanks to their sound belief in the periodic law, Ramsey and Rayleigh found a place for them at the cost of a new reversal of increasing atomic weight values and a new prediction of an intermediate element between neon and argon. A zero group was opened up that first undermined Mendeleev's notion of individual elements defined by their atomic weight. A second blow came from the discovery of electrons and radioactivity. Mendeleev desperately tried to explain this apparent anomaly with the hypothesis of confused movements of ether around heavy atoms. In this grandiose attempt to unify mechanics and chemistry, Mendeleev admitted ether in the periodic system in the 0 group. This error is instructive because it reveals the intellectual roots of Mendeleev's system. It is thus impossible to consider Mendeleev's system as a kind of precursor of quantum chemistry. Mendeleev dealt with elements and not with atoms.

Chemistry and Quantum Theory

The periodic system nevertheless served as a guide in the emergence of atomic physics, especially for Niels Bohr's (18851962) quantum model of the atom. Atoms of successive elements in the periodic system present an additional electron on the outermost shell. When a shell becomes full, a new shell begins to fill. Exceptions to this rule are reflected in the uneven length of periods in the periodic system.

The autonomy of chemistry thus seemed to be deeply questioned in the mid-twentieth century. If individual properties of chemical elements can be deduced from quantum theory, the theoretical foundations of chemistry lie in physics. Chemistry would be a reduced science. Many chemistry teachers struggle against these reductionist tendencies and claim that all the properties of chemical elements and compounds cannot be predicted by quantum calculus, even with the help of computer simulation. The bottom-up approach that prevails in recent materials chemistry and pharmaceutical research places great expectations in the control of individual atoms. However, those nanotechnologies also reveal that the chemist's ability to synthesize new products relies on a good deal of know-how and astute rules as much as on the fundamental laws of nature. Furthermore, recent synthetic strategies are more and more inspired by living organisms. For instance, supramolecular chemistry aims to design chemical processes that mimic the selectivity of biological processes to obtain molecular recognition without the help of genetic code. Thus, chemistry is renewing its old alliance with life science.

See also Alchemy ; Physics ; Science, History of ; Quantum .

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Bernadette Bensaude-Vincent

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Chemistry

Chemistry


When, in the 1830s, eight authors published Bridgewater Treatises on the goodness and wisdom of God, the series included volumes on astronomy and physics, geology, psychology, human physiology, animal and vegetable physiology, zoology, and the human hand. But chemistry was stuffed into a rag-bag of a book by William Prout (17851850) that also covered meteorology and the function of digestion. Yet this was a time when lectures on chemistry attracted large and enthusiastic audiences, and chemistry was perceived as a fundamental science. When most science was popularized in a context of natural theology, why was chemistry seen as problematic?

In the early twenty-first century, chemicals are perceived as alarming additives, the chemical industry as a source of pollution, and fertilizers, pesticides, and explosives as dangerous to the planet and its populations. Still, people depend upon plastics, synthetic fibers, pharmaceutical drugs, and paints. Chemistry is everybody's service science, ubiquitous, but highly suspect, which points to the reason for its neglect by natural theologians. Astronomers contemplate the starry heavens; chemists understand the world in order to change it.


Chemical theology in history

The alchemist was an optimist, seeing potential gold where others saw dross. Alchemists often identified the perfecting of base metal into gold with the simultaneous spiritual perfecting of the alchemical practitioner. George Herbert's well-known poem The Elixir (1633) is indeed used as a hymn. God's creation of the cosmos from chaos was compared to an alchemical project. In the laboratory, the natural improvement of base metals could be accelerated. But in the second half of the seventeenth century Robert Boyle, one of the fathers of modern chemistry, although deeply interested and involved in alchemy, delighted especially in the mechanical or corpuscular philosophy as a basis for natural theologycomparing God to a clockmaker rather than to an alchemist. He and the other founders of the Royal Society favored the plain words of artisans rather than witty metaphysical conceits or coded messages for initiates. The oblique, resonant, and metaphorical language of alchemy gave way, especially in the 1780s in the hands of chemist Antoine Lavoisier, to sober prose approximating as far as possible to algebra. For Boyle, who was deeply devout, mechanical explanations were particularly satisfying and intelligible. He bequeathed money for lectures demonstrating the existence and wisdom of God. For succeeding generations this meant astrotheology, joyfully dwelling upon Isaac Newton's work, and physico-theology, showing how humans and other creatures were like beautifully designed little clocks living in an enormous clock.

Whereas astronomy was a science of meditative observation and calculation (with spin-offs into calendars and navigation), chemistry was active and practical. The busy chemist's task was to improve the world by isolating metals, distilling medicines, or making ceramics and dyes. Adam and Eve had been expelled from paradise and sentenced to hard labor: Chemists might be able to do something about that. As the macho English chemist Humphry Davy declared in the early nineteenth century, the chemist is godlike because he exerts a "creative energy" that "entitles him to the distinction of being made in the image of God and animated by a spark of the divine mind" (p. 361). Instead of simply commending this best of all possible worlds and its designer, therefore, chemists seek to understand it in order to change it for the better, using God-given intelligence and manual skills.

Chemistry is essentially an experimental science, concerned with the secondary qualities of color, taste, and smell, and demanding trained fingers, hands, and noses; it cannot be done on paper in an armchair in a study or library. When interrogating nature through experiments, the chemist for Davy is not a passive scholar, but a master, active with his own instruments, exerting the "godlike faculties, by which reason ultimately approaches to inspiration." In the words of a poet, Davy's lectures disclosed "Nature's coyest secrets." Davy was a friend of Samuel Taylor Coleridge and other Romantic poets, and went from interrogation to worship of nature, as we see in his poems and last writings. Such pantheism was not unusual among scientists of the nineteenth century, who found religious experience in communing with nature both in the laboratory and on mountain tops.

The enthusiastic Samuel Parkes, a Unitarian and a chemical manufacturer, borrowing from church teaching called his elementary and successful book of 1806 The Chemical Catechism. Not only did he hope that parents would ensure that their children learned chemistry for its utility, he also sought to defend the youthful mind against "immorality, irreligion, and scepticism." The text (questions and answers) was amplified with footnotes, where chemical detail, poetry, and occasional encomia upon the creator were to be found. The "goodness of the ALMIGHTY" was particularly displayed in the various uses to which different substances may be put, though sometimes the "design of Nature" in assigning properties to things was not yet apparent. The book is pervaded with natural theology, rather than being an exposition of it. In a later popular work The Chemistry of Common Life (1855), widely known in translation as well as in English, the Presbyterian James Johnston concluded surprisingly that earthly life was insignificant in the vast general system of the universe. Humans were here solely because God, in a separate act of will, had formed beings to admire God's work. Johnston sought thus to indicate the insufficiency of natural theology without revelation, which told more of God's purposes and character than could ever be inferred from chemical discoveries.

Authors of Bridgewater Treatises were meant to confine themselves to natural theology, and Prout's was thus a straightforward exposition of the design argument, given a particular turn because of his idiosyncratic atomic theory. But chemistry was making rapid progress, and in 1844 George Fownes published his book Chemistry as Exemplifying the Wisdom and Benevolence of God, which was awarded the Actonian Prize associated with the Royal Institution, where Davy and Michael Faraday held forth. Fownes began from the position that recent studies (especially with microscopes, enormously improved at this time) had shown how exquisitely animals were adapted to their environment. Then he declared that recent discoveries in chemistry, especially in its organic branch, made it easier to use science to infer design. He urged people to look for God's activity in the commonplace and the everyday world, seeing God's hand in the simple laws of chemical combination, the ubiquity of protein, and the equilibria among reversible reactions that made animal and plant chemistry possible. Natural theology was for Fownes the highest aim of science. His book is also a good account of the current state of chemistry, being transformed at that time through the work especially of Justus Liebig, in whose wake German universities were training large numbers of professional research chemists to work in industry and academia.

Both Prout and Fownes came under friendly fire from George Wilson in his Religio Chemici (published posthumously in 1862) for their Panglossian emphasis upon unmixed and unbounded benevolence. Wilson, the first Professor of Technology in Edinburgh University in Scotland, was dogged by bereavements and illness, but supported by staunch religious faith. He believed that while chemical evidence, especially from the earth's atmosphere and the carbon and water cycles, demonstrated design, the demonstration of benevolence was another story. Introducing a gendered perspective, he noted that men read the Bridgewater Treatises and such books chiefly to learn science; women, more perceptive, did not because they were not impressed by such banal optimism. The problem of evil was real, and the dark side must be faced. If human bodies are constantly being renewed, why then do they wear out? Why are there poisons? Wilson noted the formidable weapons of destruction possessed by carnivores"God has been very kind to the shark"and the reality and enduring character of pain, animal and human. Evil exists alongside good, and cannot in the manner of the Manicheans be separated from it. Chemistry can show that God has love, but not that God is love. For Wilson the problem of evil is real and cannot be solved in this world, except in the light of revealed religion and true conversion. Astrotheology might be immune from such criticisms, but physico-theology along with reasoning from chemistry is undoubtedly undermined. Most of those writing natural theology had been, like William Paley, healthier and wealthier than the average person, and Wilson brought in a draft of fresh air.


The twentieth century onwards

Natural theology had made popular chemical books and lectures interesting and indeed momentous. By 1900, however, there were many students (more than in any other science) with examinations to pass and professional qualifications to gain, and their textbooks had become much drier and more factual, presenting chemical theory but not a worldview. Also, natural theology was in retreat for most of the twentieth century, under assault not only from scientific naturalists but also from theologians. And whereas chemistry had seemed a fundamental science to Davy and his contemporaries, in the early twentieth century it appeared that chemistry was being reduced to physics with the work of Ernest Rutherford and Niels Bohr. No doubt experiment was still necessary because the mathematical equations, based upon quantum theory, were too difficult to solve in detail, but genuine chemical explanation would in principle be in terms of physics, or so it seemed to physicists, who enjoyed enormous prestige. Philosophy of science, therefore, was for much of that century focused upon physics; chemistry seemed necessary, but not exciting. In addition, much nineteenth-century research had been done by individuals. In the twentieth century, the teams and groups that now undertook scientific research needed to include a chemist or two whatever their field, but the glamorous science was physics. Then came the elucidation of the DNA structure, making molecular biology and genetics major areas of interest; here, as in pharmacy, chemistry was essential, but still not the center of interest for the lay person following what was going on. In the United States, Creationism focused the attention of natural theologians upon Charles Darwin's theory of evolution by natural selection, which by the second half of the century incorporated genetics. Only perhaps in the context of ecotheology has chemistry again impinged seriously on religious thinking.

Nevertheless, chemistry was not really reduced to physics any more than architecture has been; builders must take into account the law of gravity, and chemists building molecules cannot defy the laws of physics. Working within such constraints is the basis of art in both fields. Roald Hoffmann emphasizes the creativity that lies behind structural chemistry, designing substances never made before. He also draws attention to the visual and verbal language of chemistry and the role of illustration in the science. Lavoisier's project of abolishing richness has not been achieved, and chemistry can be fun. Hoffmann has also been involved with Shira Schmidt in reflection on Jewish traditions in the light of chemistry, seeing argument as central to both and exploring dichotomies between natural and artificial, symmetry and asymmetry, purity and impurity. This is not the traditional enterprise of natural theology, as in Fownes's book, but much less formal. For the believer, satisfying parallels and analogies reveal themselves in a coherent pattern, and metaphors are refreshed.

A collective study of Science in Theistic Contexts (2001) unsurprisingly contains no discussion of chemistry. In their Gifford Lectures, however, published as Reconstructing Nature (1998), John Brooke and Geoffrey Cantor investigate the engagement (a useful word with multiple meanings) of science with religion in a historical perspective. They devote a chapter to chemistry, with particular discussion of the theological problems that can arise from the idea that the chemist is perfecting creation. They see process as a feature of chemistry that might bear upon religion. Most people accept that a world with nylon and aluminum is better than one without, and expect more progress in applied chemistry, but people remain uneasy about nineteenth-century chemist Eleanor Ormerod's enthusiastic espousal of chemical pest-control, with its aim of exterminating noxious insects. Brooke and Cantor also look at materialism and reductionism, in which chemistry has been involvedthe melancholy may be bracingly told "it's just your chemistry," and may or may not find that consoling.

What emerges is that chemistry has never been nearly as tempting for the natural theologian, wishing to put design beyond reasonable doubt, as astronomy or natural history. While the world of stinks and bangs is fun, atoms and molecules lack sublimity or accessibility. Chemistry is not only the experimental science par excellence, it is also useful in seeking to improve the world and the quality of life. That, and the idea of process, is something that should resonate with anyone pursuing natural theology, especially in an intellectual climate where the argument from design runs up against a deep prevailing skepticism. In such a broader and more sensitive natural theology, there should also be room for the metaphors and analogies from chemistry that can make it aesthetically, rather than logically, compelling.


See also Alchemy; Design; Design Argument; Ecology; Ecotheology; Natural Theology


Bibliography

boyle, robert. the vulgar notion of nature (1686), ed. m. hunter. cambridge, uk: cambridge university press, 1996.

brock, william h. from protyle to proton: william prout and the nature of matter, 17851985. bristol, uk: adam hilger, 1985.

brooke, john h., and cantor, geoffrey. reconstructing nature: the engagement of science and religion. edinburgh, uk: t&t clark, 1998.

brooke, john h.; osler, margaret j.; and van der meer, jitse m., eds. science in theistic contexts: cognitive dimensions. chicago: university of chicago press, 2001.


davy, humphry. collected works, vol. 9. london: smith elder, 18391840.

fownes, george. chemistry, as exemplifying the wisdom and beneficence of god. london: john churchill, 1844.

hoffmann, roald, and schmidt, shira leibowitz. old wine, new flasks: reflections on science and jewish tradition. new york: w. h. freeman, 1997.

hoffmann, roald, and torrence, vivian. chemistry imagined: reflections on science. washington, d.c.: smithsonian, 1993.

johnston, james f.w. the chemistry of common life. edinburgh, scotland: blackwood, 1855.

knight, david m. ideas in chemistry: a history of the science, 2nd edition. london: athlone press, 1995.

knight, david m. "higher pantheism." zygon 35 (2000): 603612.

knight, david m., and kragh, helge eds. the making of the chemist: the social history of chemistry in europe 17891914. cambridge, uk: cambridge university press, 1998.

lundgren, anders, and bensaude-vincent, bernadette, eds. communicating chemistry: textbooks and their audiences 17891939. canton, mass.: science history publications, 2000.

nye, mary jo. before big science: the pursuit of modern chemistry and physics 18001940. new york: twayne, 1996.

parkes, samuel. the chemical catechism, with notes, illustrations and experiments, 3rd edition. london: lackington allen, 1808.

prout, william. chemistry, meteorology, and the function of digestion, considered with reference to natural theology. london: william pickering, 1834.

topham, jonathan r. "beyond the 'common context': the production and reading of the bridgewater treatises." isis 89 (1998): 233262.

wilson, george. religio chemici: essays. london: macmillan, 1862.

david m. knight

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Chemistry

CHEMISTRY

CHEMISTRY is the study of the chemical and physical change of matter.

Early U.S. Chemistry and Chemical Societies

The beginning of chemistry in the United States came in the form of manufacturing goods such as glass, ink, and gunpowder. In the mid-1700s, some academic instruction in chemistry started in Philadelphia. The earliest known academic institution to formally teach chemistry was the medical school of the College of Philadelphia, where Benjamin Rush was appointed the chair of chemistry in 1769. Not only was Rush the first American chemistry teacher, he may have been the first to publish a chemistry textbook written in the United States. In 1813, the Chemical Society of Philadelphia published the first American chemical journal, Transactions. Although other chemical societies existed at that time, the Philadelphia Chemical Society was the first society to publish its own journal. Unfortunately, the journal and chemical society lasted only one year.

Sixty years later, in 1874, at Joseph Priestley's home in Northumberland, Pennsylvania, a number of renowned scientists gathered to celebrate Priestley's 1774 discovery of oxygen. It was at this gathering that Charles F. Chandler proposed the concept of an American chemical society. The proposal was turned down, in part because the American Association for the Advancement of Science (AAAS) had a chemical section that provided an adequate forum for assembly and debate. Two years later, a national society, based in New York and called the American Chemical Society, was formed with John W. Draper as its first president. Since New York chemists dominated most of the meetings and council representative positions, the Washington Chemical Society was founded in 1884 by two chemists based in Washington, D.C., Frank W. Clarke and Harvey W. Wiley. In 1890, the American Chemical Society constitution was changed to encourage the formation of local sections, such as New York, Washington, and other chemical societies in the United States, thereby leading to a national organization. By 1908, the society had approximately 3,400 members, outnumbering the German Chemical Society, which at that time was the center of world chemistry. Today, the American Chemical Society has some 163,503 members, and the United States is considered the center of world chemistry. In addition to its premier journal, the Journal of the American Chemical Society, the society also publishes several other journals that are divisional in nature, including the Journal of Organic Chemistry, Analytical Chemistry, Journal of Physical Chemistry, Inorganic Chemistry, and Biochemistry. The society also produces a publication called Chemical Abstracts, which catalogs abstracts from thousands of papers printed in chemical journals around the world.

European Influences

Although the various disciplines of chemistry—organic, inorganic, analytical, biochemistry, and physical chemistry—have a rich American history, they have also been influenced by European, especially German, chemists. The influence of physical chemistry on the development of chemistry in the United States began with American students who studied under a number of German chemists, most notably the 1909 Nobel Prize winner, Wilhelm Ostwald. In a 1946 survey by Stephen S. Visher, three of Ostwald's students were recognized as influential chemistry teachers—Gilbert N. Lewis, Arthur A. Noyes, and Theodore W. Richards. Of these three, Richards would be awarded the 1914 Nobel Prize for his contributions in accurately determining the atomic weight of a large number of chemical elements. Lewis and Noyes would go on to play a major role in the development of academic programs at institutions such as the University of California at Berkeley, the Massachusetts Institute of Technology, and Caltech. While at these institutions Lewis and Noyes attracted and trained numerous individuals, including William C. Bray, Richard C. Tolman, Joel H. Hildebrand, Merle Randall, Glenn T. Seaborg, and Linus Pauling. These individuals placed physical chemistry at the center of their academic programs and curricula. Students from these institutions, as well as other universities across America, took the knowledge they gained in physical chemistry to places like the Geophysical Laboratories, General Electric, Pittsburgh Plate Glass Company, and Bausch and Lomb.

Influence could also flow from America to Europe, as it did with one of the earliest great American chemists, J. Willard Gibbs (1839–1903). Gibbs, educated at Yale University, was the first doctor of engineering in the United States. His contribution to chemistry was in the field of thermodynamics—the study of heat and its transformations. Using thermodynamic principles, he deduced the Gibbs phase rule, which relates the number of components and phases of mixtures to the degrees of freedom in a closed system. Gibbs's work did not receive much attention in the United States due to its publication in a minor journal, but in Europe his ideas were well received by the physics community, including Wilhelm Ostwald, who translated Gibbs's work into German.

A second influence from Europe came around the 1920s, when a very bright student from Caltech named Linus Pauling went overseas as a postdoctoral fellow for eighteen months. In Europe, Pauling spent time working with Niels Bohr, Erwin Schrödinger, Arnold Sommerfeld, Walter Heitler, and Fritz London. During this time, Pauling trained himself in the new area of quantum mechanics and its application to chemical bonding. A significant part of our knowledge about the chemical bond and its properties is due to Pauling. Upon his return from Europe, Pauling went to back to Caltech and in 1950 published a paper explaining the nature of helical structures in proteins.

At the University of California at Berkeley, Gilbert N. Lewis directed a brilliant scientist, Glenn T. Seaborg. Seaborg worked as Lewis's assistant on acid-base chemistry during the day and at night he explored the mysteries of the atom. Seaborg is known for leading the first group to discover plutonium. This discovery would lead him to head a section on the top secret Manhattan Project, which created the first atomic bomb. Seaborg's second biggest achievement was his proposal to modify the periodic table to include the actinide series. This concept predicted that the fourteen actinides, including the first eleven transuranium elements, would form a transition series analogous to the rare-earth series of lanthanide elements and therefore show how the transuranium elements fit into the periodic table. Seaborg's work on the transuranium elements led to his sharing the 1951 Nobel Prize in chemistry with Edwin McMillan. In 1961, Seaborg became the chairman of the Atomic Energy Commission, where he remained for ten years.

Perhaps Seaborg's greatest contribution to chemistry in the United States was his advocacy of science and mathematics education. The cornerstone of his legacy on education is the Lawrence Hall of Science on the Berkeley campus, a public science center and institution for curriculum development and research in science and mathematics education. Seaborg also served as principal investigator of the well-known Great Explorations in Math and Science (GEMS) program, which publishes the many classes, workshops, teacher's guides, and handbooks from the Lawrence Hall of Science. To honor a brilliant career by such an outstanding individual, element 106 was named Seaborgium.

Twentieth-Century Research and Discoveries

Research in the American chemical industry started in the early twentieth century with the establishment of research laboratories such as General Electric, Eastman Kodak, AT&T, and DuPont. The research was necessary in order to replace badly needed products and chemicals that were normally obtained from Germany. Industry attracted re-search chemists from their academic labs and teaching assignments to head small, dynamic research groups. In 1909, Irving Langmuir was persuaded to leave his position as a chemistry teacher at Stevens Institute of Technology to do research at General Electric. It was not until World War I that industrial chemical research took off. Langmuir was awarded a Nobel Prize for his industrial work. In the early 1900s, chemists were working on polymer projects and free radical reactions in order to synthesize artificial rubber. DuPont hired Wallace H. Carothers, who worked on synthesizing polymers. A product of Carothers's efforts was the synthesis of nylon, which would become DuPont's greatest moneymaker. In 1951, modern organometallic chemistry began at Duquesne University in Pittsburgh with the publication of an article in the journal Nature on the synthesis of an organo-iron compound called dicyclopentadienyliron, better known as ferrocene. Professor Peter Pauson and Thomas J. Kealy, a student, were the first to publish its synthesis, and two papers would be published in 1952 with the correct predicted structure. One paper was by Robert Burns Woodward, Geoffrey Wilkinson, Myron Rosenblum, and Mark Whiting; the second was by Ernst Otto Fischer and Wolfgang Pfab. Finally, a complete crystal structure of ferrocene was published in separate papers by Phillip F. Eiland and Ray Pepinsky and by Jack D. Dunitz and Leslie E. Orgel. The X-ray crystallographic structures would confirm the earlier predicted structures. Ferrocene is a "sandwich" compound in which an iron ion is sandwiched between two cyclopentadienyl rings. The discovery of ferrocene was important in many aspects of chemistry, such as revisions in bonding concepts, synthesis of similar compounds, and uses of these compounds as new materials. Most importantly, the discovery of ferrocene has merged two distinct fields of chemistry, organic and inorganic, and led to important advances in the fields of homogeneous catalysis and polymerization.

Significant American achievements in chemistry were recognized by the Nobel Prize committee in the last part of the twentieth century and the first years of the twenty-first century. Some examples include: the 1993 award to Kary B. Mullis for his work on the polymerase chain reaction (PCR); the 1996 award to Robert F. Curl Jr. and Richard E. Smalley for their part in the discovery of C60, a form of molecular carbon; the 1998 award to John A. Pople and Walter Kohn for the development of computational methods in quantum chemistry; the 1999 award to Ahmed H. Zewail for his work on reactions using femtosecond (10-14 seconds) chemistry; the 2000 award to Alan G. MacDiarmid and Alan J. Heeger for the discovery and development of conductive polymers; and the 2001 award to William S. Knowles and K. Barry Sharpless for their work on asymmetric synthesis. The outcomes of these discoveries are leading science in the twenty-first century. The use of PCR analysis has contributed to the development of forensic science. The discovery C60 and related carbon compounds, known as nanotubes, is leading to ideas in drug delivery methods and the storage of hydrogen and carbon dioxide. The computational tools developed by Pople and Kohn are being used to assist scientists in analyzing and designing experiments. Femtosecond chemistry is providing insight into how bonds are made and broken as a chemical reaction proceeds. Heeger and MacDiarmid's work has led to what is now known as plastic electronics—devices made of conducting polymers, ranging from light-emitting diodes to flat panel displays. The work by Knowles and Sharpless has provided organic chemists with the tools to synthesize compounds that contain chirality or handedness. This has had a tremendous impact on the synthesis of drugs, agrochemicals, and petrochemicals.

BIBLIOGRAPHY

Brock, William H. The Norton History of Chemistry. New York: Norton, 1993.

———. The Chemical Tree: A History of Chemistry. New York: Norton, 2000.

Greenberg, Arthur. A Chemical History Tour: Picturing Chemistry from Alchemy to Modern Molecular Science. New York: Wiley, 2000.

Servos, John W. Physical Chemistry from Ostwald to Pauling: The Making of Science in America. Princeton, N.J.: Princeton University Press, 1990.

Jeffrey D.Madura

See alsoAmerican Association for the Advancement of Science ; Biochemistry ; Chemical Industry ; Petrochemical Industry .

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Chemistry

CHEMISTRY

CHEMISTRY. The history of early modern chemistry, understood as a body of ideas and practices related to compounding and decomposing material substances, takes us to alchemy and apothecary laboratories, artisans' workshops, metallurgists and manufacturers, scientific societies, arsenals, royal courts, and public squares. It should not be understood in terms of the victory of scientific theory over arcane beliefs, but of the changing employment of its various technologies and the contexts in and by which they were legitimized.

MATERIAL AND BODILY TECHNOLOGY

Chemistry's material technologythat is, its instruments and laboratory equipmentremained stable throughout most of the period, but was augmented by precision-oriented apparatus in the second half of the eighteenth century as the study of heat and gases, along with early industrial innovations, redirected chemical investigations. Increasingly accurate measuring devices helped bring about standardization in manufacturing ventures (e.g. Josiah Wedgwood's pottery works) while feeding debates over how to organize chemistry as an investigative enterprise. Should the heterogeneous chemical world be disciplined by analyzing qualitative or quantitative data?

The way chemical operators and investigators used their own bodies was part of this historical development and debate. As long as chemical determination rested on examining colors, smells, tastes and textures, the human senses served as crucial chemical instruments. As experimental claims increasingly relied on precise measurements by the late eighteenth century (a hallmark of the chemical revolution), sense evidence became "subjective" and, hence, a questionable foundation for proof. Chemists continued to rely on their senses, but proof became increasingly a matter of quantitative determination.

THEORY AND PRACTICE

The question of what constituted a primary chemical element was not a part of practical chemists' daily routine. Neither, prior to the late eighteenth century, was there a direct correlation between one's theoretical views and how one actually carried out chemical procedures, which can be seen by examining the impact of the mechanical philosophy on chemistry. Textbook writers such as Nicolas Lémery (16451715) attributed a substance's qualities to the shape of particles that composed it. But authors left such explanations behind when dealing with actual chemical operations. Robert Boyle (16271691), often labeled a mechanical philosopher, made a bigger impact on chemistry through his interests in practical knowledge and alchemy. Even Isaac Newton's (16421727) mechanism, which married particles to short-range forces, hardly touched chemical practicealthough theorists such as Georges-Louis Leclerc de Buffon (17071788) hoped chemical attraction (affinities) could be explained mathematically with Newtonian forces. Working chemists continued to learn their trade through apprenticeship and to be guided by practical recipes. Acquiring tacit knowledge and practical skills, then, were certainly as important for the historical development of chemistry as theoretical knowledge.

It is, however, historically important that matter theory became linked to chemical research in an increasingly instrumental way by the eighteenth century. Paracelsus (14931541), who argued for the chemical foundation of medicine (iatrochemistry), claimed that Aristotle's four elements appeared in bodies as mercury, sulfur, and salt. Mercury was the principle of volatility and fusibility, sulfur of inflammability, and salt of incombustibility. Therefore, chemists might recognize a compound not only as heavy or wet, but also as liable to specific chemical processes.

Johann Joachim Becher (16351682) substituted three categories of earth for Paracelsus's principles and explained material change largely in terms of their combination with and release from compounds through processes such as combustion. His student George Ernst Stahl (16601734) further codified Becher's work, giving the name "phlogiston" (from the Greek verb "to inflame") to Becher's terra pinguis (the sulfur of inflammability) and teaching that phlogiston's presence was responsible for characteristics including metallicity, color, and inflammability. In France, the influential chemistry lecturer Guillaume François Rouelle (17031770) popularized the idea of phlogiston, associating it with fire. Others such as Joseph Priestley (17331804) identified it variously with electricity and hydrogen. Phlogiston was used to explain phenomena including combustion, calcination, and the quality of air, thereby organizing a number of research activities under a set of interconnecting theories and emphasizing the potential reversibility of chemical processes.

Others began considering the Aristotelian elements as material instruments. Stephen Hales (16771761) focused on the expansion of air and the way in which it could become "fixed" in bodies. Herman Boerhaave (16681738) went further, organizing his chemistry lectures largely around the investigative consequences of considering earth, water, air, and fire as instruments that afforded specific chemical processes. A Newtonian by public pronouncement, Boerhaave actually did much more to stimulate chemical research by focusing on the reactive effects of these elemental instruments. He related fire (the substance of heat) to the primary processes of expansion and repulsion. He presented air and water as providing containers in which other particles were suspended. It wasn't long before these "instruments" themselves were subjected to chemical analysis, as investigators sought to understand whether their "instrumental" presence was chemically passive or active. Research in the second half of the eighteenth century was marked by investigations of newly discovered gases (qualitatively distinct "airs"), the role of heat, and, in the 1780s, the composition of water.

LITERARY TECHNOLOGY

Chemical theory and instrumental research practices were also linked in the way chemical knowledge came to be organized nomenclaturally and in analytical tables (chemistry's literary technology). Related to the heritage of alchemy and the various contexts in which chemical substances were discovered and used, chemical nomenclature was traditionally a colorfully unsystematic affair. Growing interest in chemical research in the second half of the eighteenth century, especially the investigation of a number of new "airs," led chemists to consider nomenclatural reform. Standard conventions for naming new substances would allow researchers from various communities to communicate. In 1787 Antoine Laurent Lavoisier (17431794), Louis Bernard Guyton de Morveau (17371816), Antoine François Fourcroy (17551809), and Claude Simon Berthollet (17481822) revamped chemistry's nomenclature totally, enunciating in their Méthode de nomenclature chimique a revolutionary way to structure chemistry's investigative knowledge and practices.

Oxygen's discovery and naming provides a good example. Recognized in the 1770s as a distinct "air" responsible for combustion, supporting respiration, and the process of calcination, it was variously named the "purest part of air," "fire air," "eminently respirable air," and "dephlogisticated air." Lavoisier focused on what he considered its most far-reaching characteristic and argued that it should be called "oxygen," the "generator" of acids. Not only did he use oxygen's causal properties to argue against the existence of phlogiston, he named the substance in a way that simultaneously reflected how the relation between these properties ought to be understood and how chemists ought to pursue future research.

Traditionally, the secretive nature of many alchemical and artisanal practices had combined with chemistry's lack of institutional and disciplinary unity to work against the development of a public, systematic means of recording compositional data. This began changing when Étienne François Geoffroy (16721731) presented his "Table of the different relationships observed between different substances" to the French Academy of Sciences in 1718. Recording and publishing these relationships, often called affinities, provided a handy way for chemists to share and expand empirical knowledge without having to agree on their theoretical explanation. As the century progressed, affinity and solvent tables became more sophisticated (recording, for example, how relations were observed), leading chemists to hope that their field might thereby gain the certainty of a scientific discipline. As was true with nomenclatural reform, this was largely achieved by Lavoisier and his colleagues, with revolutionary results. Lavoisier's 1789 textbook Traitéélémentaire de chimie included tables whose structures redirected research along the same lines as chemistry's new nomenclature.

Lavoisier began his textbook by arguing that humans live in a Condillacian world; chemists should therefore build their discipline on a foundation of sensible facts. Chemistry's nomenclature should express only what chemists actively observed; its basic elements should be defined by laboratory procedures. In fact, Lavoisier began his "table of simple substances" with five elements that could never be isolated, but which he made responsible for fundamental chemical processes. Oxygen "generates" acidity, hydrogen "generates" water. Caloric, the substance of heat, interacts with chemical affinities to regulate composition and decomposition. In place of affinity and solvent tables, Lavoisier filled his textbook with tables that simultaneously recorded and predicted the combinatorial powers of elements such as oxygen. Together they formed an integrated research program intended to discipline chemistry.

CHEMISTRY'S INSTRUMENTALIZATION

Lavoisier's laboratory practices reflected what appeared on the pages of his book, the last third of which treated laboratory instruments. If primary elements couldn't be isolated, Lavoisier argued that their active presence could be quantitatively traced. Unmeasurable phlogiston was out, precision balances were in, as seen in his proof that water is compounded of hydrogen and oxygen. Affinities could not yet be quantified, but the effect of caloric on composition and decomposition could be quantitatively inferred by the melting of ice in an ice calorimeteran instrument designed by Lavoisier. In general, nomenclature, instrumental theory, and measurement provided a research program for future chemists, in terms of both questions and methods for resolving them.

This culmination of chemistry's instrumentalization was, arguably, the essence of the chemical revolution. Whether others adopted Lavoisier's theories or followed the specifics of his research proposals, the modern discipline of chemistry was permanently marked by the instrumental bounds he prescibed.

See also Alchemy ; Apothecaries ; Boerhaave, Herman ; Boyle, Robert ; Lavoisier, Antoine ; Paracelsus ; Priestley, Joseph .

BIBLIOGRAPHY

Bensaude-Vincent, Bernadette. Lavoisier. Memoires d'une révolution. Paris, 1993.

Golinski, Jan. Science as Public Culture: Chemistry and Enlightenment in Britain 17601820. Cambridge, U.K., 1992.

Hannaway, Owen. The Chemist and the Word: The Didactic Origins of Chemistry. Baltimore, 1985.

Holmes, Frederick Lawrence. Eighteenth-Century Chemistry as an Investigative Enterprise. Berkeley, 1989.

Roberts, Lissa. "The Death of the Sensuous Chemist: the 'New' Chemistry and the Transformation of Sensuous Technology." Studies in History and Philosophy of Science 26 (1995): 503529.

. "Setting the Table: The Disciplinary Development of Eighteenth-Century Chemistry as Read through the Changing Structure of its Tables." In The Literary Structure of Scientific Argument, edited by Peter Dear, pp. 99132. Philadelphia, 1991.

Lissa Roberts

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Chemistry

Chemistry

Chemistry is the study of the composition of matter and the changes that take place in that composition. If you place a bar of iron outside your window, the iron will soon begin to rust. If you pour vinegar on baking soda, the mixture fizzes. If you hold a sugar cube over a flame, the sugar begins to turn brown and give off steam. The goal of chemistry is to understand the composition of substances such as iron, vinegar, baking soda, and sugar and to understand what happens during the changes described here.

History

Both the term chemistry and the subject itself grew out of an earlier field of study known as alchemy. Alchemy has been described as a kind of pre-chemistry, in which scholars studied the nature of matterbut without the formal scientific approach that modern chemists use. The term alchemy is probably based on the Arabic name for Egypt, al-Kimia, or the "black country."

Ancient scholars learned a great deal about matter, usually by trial- and-error methods. For example, the Egyptians mastered many technical procedures such as making different types of metals, manufacturing colored glass, dying cloth, and extracting oils from plants. Alchemists of the Middle Ages (4001450) discovered a number of elements and compounds and perfected other chemical techniques, such as distillation (purifying a liquid) and crystallization (solidifying substances into crystals).

Words to Know

Analytical chemistry: That area of chemistry that develops ways to identify substances and to separate and measure the components in a compound or mixture.

Inorganic chemistry: The study of the chemistry of all the elements in the periodic table except for carbon.

Organic chemistry: The study of the chemistry of carbon compounds.

Physical chemistry: The branch of chemistry that investigates the properties of materials and relates these properties to the structure of the substance.

Qualitative analysis: The analysis of compounds and mixtures to determine the elements present in a sample.

Quantitative analysis: The analysis of compounds and mixtures to determine the percentage of elements present in a sample.

The modern subject of chemistry did not appear, however, until the eighteenth century. At that point, scholars began to recognize that research on the nature of matter had to be conducted according to certain specific rules. Among these rules was one stating that ideas in chemistry had to be subjected to experimental tests. Some of the founders of modern chemistry include English natural philosopher Robert Boyle (16271691), who set down certain rules on chemical experimentation; Swedish chemist Jöns Jakob Berzelius (17791848), who devised chemical symbols, determined atomic weights, and discovered several new elements; English chemist John Dalton (17661844), who proposed the first modern atomic theory; and French chemist Antoine-Laurent Lavoisier (17431794), who first explained correctly the process of combustion (or burning), established modern terminology for chemicals, and is generally regarded as the father of modern chemistry.

Goals of chemistry

Chemists have two major goals. One is to find out the composition of matter: to learn what elements are present in a given sample and in what percentage and arrangement. This type of research is known as analysis. A second goal is to invent new substances that replicate or that are

different from those found in nature. This form of research is known as synthesis. In many cases, analysis leads to synthesis. That is, chemists may find that some naturally occurring substance is a good painkiller. That discovery may suggest new avenues of research that will lead to a synthetic (human-made) product similar to the natural product, but with other desirable properties (and usually lower cost). Many of the substances that chemistry has produced for human use have been developed by this process of analysis and synthesis.

Fields of chemistry

Today, the science of chemistry is often divided into four major areas: organic, inorganic, physical, and analytical chemistry. Each discipline investigates a different aspect of the properties and reactions of matter.

Organic chemistry. Organic chemistry is the study of carbon compounds. That definition sometimes puzzles beginning chemistry students because more than 100 chemical elements are known. How does it happen that one large field of chemistry is devoted to the study of only one of those elements and its compounds?

The answer to that question is that carbon is a most unusual element. It is the only element whose atoms are able to combine with each other in apparently endless combinations. Many organic compounds consist of dozens, hundreds, or even thousands of carbon atoms joined to each other in a continuous chain. Other organic compounds consist of carbon chains with other carbon chains branching off them. Still other organic compounds consist of carbon atoms arranged in rings, cages, spheres, or other geometric forms.

The scope of organic chemistry can be appreciated by knowing that more than 90 percent of all compounds known to science (more than 10 million compounds) are organic compounds.

Organic chemistry is of special interest because it deals with many of the compounds that we encounter in our everyday lives: natural and synthetic rubber, vitamins, carbohydrates, proteins, fats and oils, cloth, plastics, paper, and most of the compounds that make up all living organisms, from simple one-cell bacteria to the most complex plants and animals.

Inorganic chemistry. Inorganic chemistry is the study of the chemistry of all the elements in the periodic table except for carbon. Like their cousins in the field of organic chemistry, inorganic chemists have provided the world with countless numbers of useful products, including fertilizers, alloys, ceramics, household cleaning products, building materials, water softening and purification systems, paints and stains, computer chips and other electronic components, and beauty products.

The more than 100 elements included in the field of inorganic chemistry have a staggering variety of properties. Some are gases, others are solid, and a few are liquid. Some are so reactive that they have to be stored in special containers, while others are so inert (inactive) that they virtually never react with other elements. Some are so common they can be produced for only a few cents a pound, while others are so rare that they cost hundreds of dollars an ounce.

Because of this wide variety of elements and properties, most inorganic chemists concentrate on a single element or family of elements or on certain types of reactions.

Physical chemistry. Physical chemistry is the branch of chemistry that investigates the physical properties of materials and relates these properties to the structure of the substance. Physical chemists study both

organic and inorganic compounds and measure such variables as the temperature needed to liquefy a solid, the energy of the light absorbed by a substance, and the heat required to accomplish a chemical transformation. A computer is used to calculate the properties of a material and compare these assumptions to laboratory measurements. Physical chemistry is responsible for the theories and understanding of the physical phenomena utilized in organic and inorganic chemistry.

Analytical chemistry. Analytical chemistry is that field of chemistry concerned with the identification of materials and with the determination of the percentage composition of compounds and mixtures. These two lines of research are known, respectively, as qualitative analysis and quantitative analysis. Two of the oldest techniques used in analytical chemistry are gravimetric and volumetric analysis. Gravimetric analysis refers to the process by which a substance is precipitated (changed to a solid) out of solution and then dried and weighed. Volumetric analysis involves the reaction between two liquids in order to determine the composition of one or both of the liquids.

In the last half of the twentieth century, a number of mechanical systems have been developed for use in analytical research. For example, spectroscopy is the process by which an unknown sample is excited (or energized) by heating or by some other process. The radiation given off by the hot sample can then be analyzed to determine what elements are present. Various forms of spectroscopy are available (X-ray, infrared, and ultraviolet, for example) depending on the form of radiation analyzed.

Other analytical techniques now in use include optical and electron microscopy, nuclear magnetic resonance (MRI; used to produce a three-dimensional image), mass spectrometry (used to identify and find out the mass of particles contained in a mixture), and various forms of chromatography (used to identify the components of mixtures).

Other fields of chemistry. The division of chemistry into four major fields is in some ways misleading and inaccurate. In the first place, each of these four fields is so large that no chemist is an authority in any one field. An inorganic chemist might specialize in the chemistry of sulfur, the chemistry of nitrogen, the chemistry of the inert gases, or in even more specialized topics.

Secondly, many fields have developed within one of the four major areas, and many other fields cross two or more of the major areas. For an example of specialization, the subject of biochemistry is considered a subspecialty of organic chemistry. It is concerned with organic compounds that occur within living systems. An example of a cross-discipline subject is bioinorganic chemistry. Bioinorganic chemistry is the science dealing with the role of inorganic elements and their compounds (such as iron, copper, and sulfur) in living organisms.

At present, chemists explore the boundaries of chemistry and its connections with other sciences, such as biology, environmental science, geology, mathematics, and physics. A chemist today may even have a socalled nontraditional occupation. He or she may be a pharmaceutical salesperson, a technical writer, a science librarian, an investment broker, or a patent lawyer, since discoveries by a traditional chemist may expand and diversify into a variety of fields that encompass our whole society.

[See also Alchemy; Mass spectrometry; Organic chemistry; Qualitative analysis; Quantitative analysis; Spectroscopy ]

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chemistry

chemistry, branch of science concerned with the properties, composition, and structure of substances and the changes they undergo when they combine or react under specified conditions.

Branches of Chemistry

Chemistry can be divided into branches according to either the substances studied or the types of study conducted. The primary division of the first type is between inorganic chemistry and organic chemistry. Divisions of the second type are physical chemistry and analytical chemistry.

The original distinction between organic and inorganic chemistry arose as chemists gradually realized that compounds of biological origin were quite different in their general properties from those of mineral origin; organic chemistry was defined as the study of substances produced by living organisms. However, when it was discovered in the 19th cent. that organic molecules can be produced artificially in the laboratory, this definition had to be abandoned. Organic chemistry is most simply defined as the study of the compounds of carbon. Inorganic chemistry is the study of chemical elements and their compounds (with the exception of carbon compounds).

Physical chemistry is concerned with the physical properties of materials, such as their electrical and magnetic behavior and their interaction with electromagnetic fields. Subcategories within physical chemistry are thermochemistry, electrochemistry, and chemical kinetics. Thermochemistry is the investigation of the changes in energy and entropy that occur during chemical reactions and phase transformations (see states of matter). Electrochemistry concerns the effects of electricity on chemical changes and interconversions of electric and chemical energy such as that in a voltaic cell. Chemical kinetics is concerned with the details of chemical reactions and of how equilibrium is reached between the products and reactants.

Analytical chemistry is a collection of techniques that allows exact laboratory determination of the composition of a given sample of material. In qualitative analysis all the atoms and molecules present are identified, with particular attention to trace elements. In quantitative analysis the exact weight of each constituent is obtained as well. Stoichiometry is the branch of chemistry concerned with the weights of the chemicals participating in chemical reactions. See also chemical analysis.

History of Chemistry

The earliest practical knowledge of chemistry was concerned with metallurgy, pottery, and dyes; these crafts were developed with considerable skill, but with no understanding of the principles involved, as early as 3500 BC in Egypt and Mesopotamia. The basic ideas of element and compound were first formulated by the Greek philosophers during the period from 500 to 300 BC Opinion varied, but it was generally believed that four elements (fire, air, water, and earth) combined to form all things. Aristotle's definition of a simple body as "one into which other bodies can be decomposed and which itself is not capable of being divided" is close to the modern definition of element.

About the beginning of the Christian era in Alexandria, the ancient Egyptian industrial arts and Greek philosophical speculations were fused into a new science. The beginnings of chemistry, or alchemy, as it was first known, are mingled with occultism and magic. Interests of the period were the transmutation of base metals into gold, the imitation of precious gems, and the search for the elixir of life, thought to grant immortality. Muslim conquests in the 7th cent. AD diffused the remains of Hellenistic civilization to the Arab world. The first chemical treatises to become well known in Europe were Latin translations of Arabic works, made in Spain c.AD 1100; hence it is often erroneously supposed that chemistry originated among the Arabs. Alchemy developed extensively during the Middle Ages, cultivated largely by itinerant scholars who wandered over Europe looking for patrons.

Evolution of Modern Chemistry

In the hands of the "Oxford Chemists" (Robert Boyle, Robert Hooke, and John Mayow) chemistry began to emerge as distinct from the pseudoscience of alchemy. Boyle (1627–91) is often called the founder of modern chemistry (an honor sometimes also given Antoine Lavoisier, 1743–94). He performed experiments under reduced pressure, using an air pump, and discovered that volume and pressure are inversely related in gases (see gas laws). Hooke gave the first rational explanation of combustion—as combination with air—while Mayow studied animal respiration. Even as the English chemists were moving toward the correct theory of combustion, two Germans, J. J. Becher and G. E. Stahl, introduced the false phlogiston theory of combustion, which held that the substance phlogiston is contained in all combustible bodies and escapes when the bodies burn.

The discovery of various gases and the analysis of air as a mixture of gases occurred during the phlogiston period. Carbon dioxide, first described by J. B. van Helmont and rediscovered by Joseph Black in 1754, was originally called fixed air. Hydrogen, discovered by Boyle and carefully studied by Henry Cavendish, was called inflammable air and was sometimes identified with phlogiston itself. Cavendish also showed that the explosion of hydrogen and oxygen produces water. C. W. Scheele found that air is composed of two fluids, only one of which supports combustion. He was the first to obtain pure oxygen (1771–73), although he did not recognize it as an element. Joseph Priestley independently discovered oxygen by heating the red oxide of mercury with a burning glass; he was the last great defender of the phlogiston theory.

The work of Priestley, Black, and Cavendish was radically reinterpreted by Lavoisier, who did for chemistry what Newton had done for physics a century before. He made no important new discoveries of his own; rather, he was a theoretician. He recognized the true nature of combustion, introduced a new chemical nomenclature, and wrote the first modern chemistry textbook. He erroneously believed that all acids contain oxygen.

Impact of the Atomic Theory

The assumption that compounds were of definite composition was implicit in 18th-century chemistry. J. L. Proust formally stated the law of constant proportions in 1797. C. L. Berthollet opposed this law, holding that composition depended on the method of preparation. The issue was resolved in favor of Proust by John Dalton's atomic theory (1808). The atomic theory goes back to the Greeks, but it did not prove fruitful in chemistry until Dalton ascribed relative weights to the atoms of chemical elements. Electrochemical theories of chemical combinations were developed by Humphry Davy and J. J. Berzelius. Davy discovered the alkali metals by passing an electric current through their molten oxides. Michael Faraday discovered that a definite quantity of charge must flow in order to deposit a given weight of material in solution. Amedeo Avogadro introduced the hypothesis that equal volumes of gases at the same pressure and temperature contain the same number of molecules.

William Prout suggested that as all elements seemed to have atomic weights that were multiples of the atomic weight of hydrogen, they could all be in some way different combinations of hydrogen atoms. This contributed to the concept of the periodic table of the elements, the culmination of a long effort to find regular, systematic properties among the elements. Periodic laws were put forward almost simultaneously and independently by J. L. Meyer in Germany and D. I. Mendeleev in Russia (1869). An early triumph of the new theory was the discovery of new elements that fit the empty spaces in the table. William Ramsay's discovery, in collaboration with Lord Rayleigh, of argon and other inert gases in the atmosphere extended the periodic table

Organic Chemistry and the Modern Era

Organic chemistry developed extensively in the 19th cent., prompted in part by Friedrich Wohler's synthesis of urea (1828), which disproved the belief that only living organisms could produce organic molecules. Other important organic chemists include Justus von Liebig, C. A. Wurtz, and J. B. Dumas. In 1852 Edward Frankland introduced the idea of valency (see valence), and in 1858 F. A. Kekule showed that carbon atoms are tetravalent and are linked together in chains. Kekule's ring structure for benzene opened the way to modern theories of organic chemistry. Henri Louis Le Châtelier, J. H. van't Hoff, and Wilhelm Ostwald pioneered the application of thermodynamics to chemistry. Further contributions were the phase rule of J. W. Gibbs, the ionization equilibrium theory of S. A. Arrhenius, and the heat theorem of Walther Nernst. Ernst Fischer's work on the amino acids marks the beginning of molecular biology.

At the end of the 19th cent., the discovery of the electron by J. J. Thomson and of radioactivity by A. E. Becquerel revealed the close connection between chemistry and physics. The work of Ernest Rutherford, H. G. J. Moseley, and Niels Bohr on atomic structure (see atom) was applied to molecular structures. G. N. Lewis, Irving Langmuir, and Linus Pauling developed the electronic theory of chemical bonds, directed valency, and molecular orbitals (see molecular orbital theory). Transmutation of the elements, first achieved by Rutherford, has led to the creation of elements not found in nature; in work pioneered by Glenn Seaborg elements heavier than uranium have been produced. With the rapid development of polymer chemistry after World War II a host of new synthetic fibers and materials have been added to the market. A fuller understanding of the relation between the structure of molecules and their properties has allowed chemists to tailor predictively new materials to meet specific needs.

Bibliography

See I. Asimov, A Short History of Chemistry (1965); D. A. McQuarrie and P. A. Rock, General Chemistry (1984); L. Pauling, General Chemistry (3d ed. 1991); R. C. Weast, ed., CRC Handbook of Chemistry and Physics (published annually).

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Chemistry

Chemistry

The field of chemistry requires the use of computers in a multitude of ways. Primarily, computers are useful for storing vast amounts of data for the researcher or student to use. From facts about the periodic table to displaying 3-D models of molecules for easy visualization, computers are vital in the chemistry lab.

Equally important, many aspects of chemistry are explained in mathematical terms, and mathematicians have applied the laws of physics to much of chemistry. The result of this work is a diversity of equations that define chemical properties and predict chemical reactions. Because of these equations, for example, one can figure out the volume and density of gases. Equations are also used to calculate atmospheric pressures or to figure out the molecular weight of a solute (dissolved substance) in a solvent.

Typically, chemistry software applications include a multitude of equations. Some equations are quite complex. Using an equation engine, much like a search engine, allows the user to search for equations and bring them to the desktop in a format that allows for the insertion of values. Because the chemist does not need to recopy complex equations and constants, equation engines save time as well as decrease the chance of errors. Computers then allow the easy and accurate processing of this information.

Computers are so necessary in chemistry that some colleges and universities require chemistry majors to take courses in computer science. The chemist must gain proficiency in using word processors and constructing spreadsheets for presentations. Statistics, statistical methods, and scientific graphing are also important elements in chemistry. Many students learn computer programming to become comfortable with a variety of operating systems. Familiarity with utility programs, networking, and network software is essential. Some knowledge of graphic design allows for the demonstration and manipulation of chemical principles, for example, in molecular modeling.

More and more instruments for chemists are being designed to work seamlessly with computers. Tools such as mass spectrometers are being interfaced with computers to allow for fast and accurate presentation of complex data. A thorough knowledge of computer architecture allows the chemist to interface these instruments if such interfacing is not readily available. The field of chemistry is also ideally suited to computer assisted instruction. Some universities, such as the University of Massachusetts, market general chemistry courses on CD-ROM (compact disc-read only memory).

Not only are computers helpful as a resource but they can also cut costs, time, and errors in the classroom. For instance, biochemistry students might want to participate in an experiment to study the structure-function relationship of a polypeptide (including the study of the structure of the polypeptide using an amino acid analyzer and peptide sequencer). The cost of conducting such an experimentapproximately $200,000can be a major drawback. The time constraints, even if the study runs smoothly, can also exceed the limits of a single semester course. Computer simulation, however, can make the process much easier and more cost effective. Also, the student's attention can be focused on a specific point of interest instead of being distracted by the endless details involved in the actual experiment.

Computational chemistry is similar to molecular modeling . Both consist of the interactive combination of visualization and computational techniques. Molecular modeling keeps the emphasis of the work on the visualization of the molecule. Computational chemistry concentrates on the computational techniques. A fine illustration of the use of computers and the Internet with molecular (DNA) modeling was constructed by James Watson of Clare College and Francis Crik of Gonville and Caius College, in Cambridge, England.

Chemists, like scientists in other fields, are growing increasingly dependent upon the Internet. The World Wide Web, and especially e-mail, allows instant mass communication between teachers and students, as well as the isolated chemist and his or her colleagues. Online professional journals are becoming more common, allowing scientists to review literature more easily. The first online chemistry conference was held in 1993 by the American Chemical Society. Online classes are being offered more frequently. The Internet also allows scientists to collaborate on projects with each other without necessarily working in the same building, or even the same continent. The Internet makes it far easier for individuals to participate in professional organizations.

Database management is essential to chemistry. Many databases evolve too quickly and are too extensive to be maintained by a single chemist. The National Institutes of Health (NIH) is a major supplier of resources for molecular modeling for researchers. The Center for Molecular Modeling is part of the Division of Computational Bioscience, Center for Informational Technology. At this web site, computational chemists work with researchers on the relationships between structure and function of molecules. This allows researchers to develop a greater understanding of chemical interactions, enzyme production, ion bonds, and other properties of molecules.

The Internet is also a wonderful resource for students and educators of chemistry. Web resources include tutorials and reference sites for almost all fields and levels of chemistry students, from high school and college. One site, the Schlumberger SEED, or the Science Excellence in Educational Development web site, promotes the science and technology to students by introducing lab experiments, providing science news, offering help to teachers, and hosting a question and answer forum. This site offers another forum for one-on-one communication between future scientists and those actively working in the field.

Some chemists have decided that the computer and Internet can allow them to make chemistry entertaining. For example, John P. Selegue and F. James Holler of the University of Kentucky have put their research and technical skills to use by composing a web page that explores the use of the elements of the periodic table (even molybdenum) throughout the history of comic books. This site was one of the winners of the 2001 Scientific American's Sci/Tech Web Awards.

see also Computer Assisted Instruction; Molecular Biology; Physics; Scientific Visualization.

Mary McIver Puthawala

Internet Resources

The Chemistry Place. Needham, MA: Peregrine Publishers, Inc. <http://www.chemplace.com>

Schlumberger SEED, The Science Education Web Site. <http://www.slb.com/seed/>

Selegue, John P., and F. James Holler. The Comic Book Periodic Table of the Elements. <http://www.uky.edu/Projects/Chemcomics/>

Watson, James, and Francis Crik. DNA and RNA Structures. <http://www.ch.cam.ac.uk/SGTL/Structures/nucleic/>

Zielinski, Theresa Julia, and Mary L. Swift. "What Every Chemist Should Know About Computers, II." The Chemical Educator 2, no.3 (1996). <http://link.springer-ny.com/link/service/journals/00897/sbibs/s0002003/spapers/23tjz897.htm>

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Chemistry

Chemistry

Chemistry deals with the study of the properties and reactions of atoms and molecules. In particular, chemistry deals with reaction processes and the energy transition. Major divisions of chemistry include inorganic chemistry, organic chemistry (chemistry of carbon based compounds), physical chemistry, analytical chemistry, and biochemistry. Geochemistry deals with the reaction unique to geological processes.

The origin of the modern science of chemistry is often attributed to the work of French physicist and chemist Antoine Lavoisier (17431794). In 1774, Lavoisier demonstrated that oxygen is a critical component of air needed for combustion. This observation led into a better understanding of the changes in composition and structure of matter. Lavoisier's publication of the first list of elemental substances eventually evolved into the Periodic table of the elements. Other important contributions to early chemistry include British chemist and physicist John Dalton's (17661844) atomic theory ; Italian physicist and chemist Amedeo Avogadro's (17761856) theory that molecules are made up of atoms; and Sir Edward Frankland's (18251899) descriptions of chemical reactions. These observations and theories all led to the portrayal of chemistry as the architecture of molecules.

Each discipline of chemistry (e.g., inorganic, analytical, physical chemistry, etc.) studies a different facet of the structure and composition of materials and their changes in composition and energy. As molecules and scientific problems become more complex, the traditional areas of chemical investigation begin to overlap with other physical sciences.

Organic chemistry is the study of compounds that contain carbon atoms. The term organic was first introduced by the Swedish scientist, Jöns Jacob Berzelius (17791848) to refer to substances isolated from living systems. Inorganic compounds, a call predominant in geological processes, are those isolated from nonliving sources. At the time, it was believed that a "vital force" only present in living systems was necessary for the preparation of organic compounds. In 1828, German chemist Friedrich Wöhler (18001882) first synthesized urea, an organic compound isolated from urine, by evaporating a water solution of the inorganic compound ammonium cyanate. Eventually, the vital force theories (e.g., those based on the idea that life and the chemistry of life depended upon an undefined vital force peculiar to living organisms) were discarded and organic chemistry became the investigation of the over seven million carbon-containing compounds. Today, organic chemists work primarily to synthesize new molecules to be used in pharmaceuticals, surfactants, paints, and coatings. They are also involved in scaling reactions from grams to tons in industrial research laboratories.

Inorganic compounds, at the time of the vital force theories, were those materials isolated from nonliving sources. Now, inorganic chemistry is the chemistry of all the elements except for carbon. This includes the chemistry of transition metals which coordinate with organic ligands and make up hemoglobin; the very reactive alkali metals used to make organometallic compounds in the manufacture of pharmaceutical materials; and also, the semi-metallic elements that have unusual electronic properties used in solar cells for the conversion of light into electricity . Inorganic chemists find employment in the production of glass , ceramics, semi-conductors, and advanced synthetic catalysts.

In 1909, German scientist Wilhelm Ostwald (18531932) was awarded the Nobel Prize in Chemistry for his work with catalysis, a very useful technique in industrial manufacturing. Ostwald is often referred to as the father of physical chemistry, a branch of chemistry devoted to the investigation of the underlying physical processes responsible for chemical properties and phenomena. Physical chemistry describes the influence of temperature , pressure, concentration, and catalyst used in organic and inorganic reactions. These data give important insight into the mechanisms of the chemical change and predict the best experimental methodology for a specific manufacturing process. Physical chemists are employed in industrial, academic, and governmental laboratories to study and calculate the fundamental properties of elements and molecular compounds. The application of physical chemistry is critical to the development of efficient devices, new applications of chemicals and better methods for measuring chemical phenomena.

Analytical chemistry is the branch of chemistry involved with the measurement and characterization of materials. Chemical analysis is divided into classical and instrumental methods. Wet or classical chemical analysis is the oldest form of analytical chemistry and involves the use of chemical reactions utilizing gravimetric and volumetric methodology to analyze material compositions. The use of instrumental methods for analytical analysis provides comprehensive information about chemical structure. Instrumental techniques include methods for measuring molecular spectroscopy such as infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), mass spectroscopy (MS), and x-ray crystallography. Gas chromatography, liquid chromatography, and electrophoresis are examples of separation methods used by analytical chemists. There is a need for analytical chemists in governmental, industrial, and academic research organizations to characterize new materials and determine the chemical composition of materials.

Chemists often work with geologists and geophysicists, in an effort to identify specific geologic reactions or to help characterize a specific geologic formation.

See also Atmospheric chemistry; Bowen's reaction series; Dating methods; Petroleum detection; Petroleum, economic uses of; Petroleum extraction; Weathering and weathering series

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chemistry

chemistry Branch of science concerned with the properties, structure and composition of substances and their reactions with one another. Inorganic chemistry studies the preparation, properties and reactions of all chemical elements and their compounds, except those of carbon. Organic chemistry studies the reactions of carbon compounds, which are c.100 times more numerous than nonorganic ones. It also studies an immense variety of molecules, including those of industrial compounds such as plastics, rubbers, dyes, drugs and solvents. Biochemistry deals with living processes and Analytical chemistry deals with the composition of substances. Physical chemistry deals with the physical properties of substances, such as their boiling and melting points. Its subdivisions include electrochemistry, thermochemistry and chemical kinetics.

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chemistry

chem·is·try / ˈkeməstrē/ (abbr.: chem.) • n. (pl. -tries) 1. the branch of science that deals with the identification of the substances of which matter is composed; the investigation of their properties and the ways in which they interact, combine, and change; and the use of these processes to form new substances. ∎  the chemical composition and properties of a substance or body: the chemistry of soil | the chemistries of other galaxies. ∎ fig. a complex entity or process: the chemistry of politics. 2. the emotional or psychological interaction between two people, esp. when experienced as a powerful mutual attraction: their affair was triggered by intense sexual chemistry.

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chemistry

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