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ScienceWeek
FOUNDATIONS OF MODERN CHEMISTRY
ON THE DEVELOPMENT OF CHEMISTRY
When we study the history of science, it is useful to direct our attention to the intellectual obstruction which, at a given moment, is checking the progress of thought -- the hurdle which it was then particularly necessary for the mind to surmount.
In chemistry, it would seem that the difficulty in the 17th and 18th centuries lay in certain primary things which are homely and familiar -- things which would not trouble a schoolboy in the 20th century, so that it is not easy for us to see why our predecessors should seem to have been so obtuse. It was necessary in the first place that they should be able to identify the chemical elements, but the simplest examples were perhaps the most difficult of all. For thousands of years, air, water, and fire had been wrapped up in a myth somewhat similar to the myth of the special ethereal substance out of which the heavenly bodies and celestial spheres were thought to have been made. Of all the things in the world, air and water seemed most certain to be irreducible elements.
Even fire seemed to be another element -- hidden in many substances, but released during combustion, and visibly making its escape in the form of flame. Francis Bacon (1561-1626) and some of his successors in the 17th century had conjectured that heat might be a form of motion in microscopic particles of matter. Mixed up with such conjectures, however, we find the view that it was itself a material substance; and this latter view was to prevail in the 18th century.
Men who had made great advances in metallurgy, and had accumulated much knowledge of elaborate and complicated chemical interactions, were as yet unable to straighten out their ideas on these apparently simple topics. It would appear to us today that chemistry could not be established on a proper footing until a satisfactory starting-point could be discovered for the understanding of air and water; and for this to be achieved it would seem to been necessary to have a more adequate idea both about the existence of "gases" and about the process of combustion. The whole development depended on the recognition and the weighing of gases; but at the opening of the 18th century there was no realization of the distinctions between gases, no instrument for collecting a gas, and no sufficient consciousness of the fact that the measurements of weight might play the decisive part amongst the data of chemistry."
Adapted from: Herbert Butterfield: The Origins of Modern Science 1300-1800. G. Bell & Sons 1957.
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ON GASES AND THE FOUNDATION OF MODERN CHEMISTRY
It is interesting that it was not until the early years of the 17th century that the word "gas" was used. This word was invented by a Belgian physician, J.B. van Helmont (1579-1644), to fill the need caused by the new idea that different kinds of "airs" existed. Van Helmont discovered that a gas (the gas that we now call carbon dioxide) is formed when limestone is treated with acid, and that this gas differs from air in that when respired it does not support life and that it is heavier than air. He also found that the same gas is produced by fermentation, and that it is present in the Grotto del Cane, a cave in Italy in which dogs were observed to become unconscious (carbon dioxide escaping from fissures in the floor displaces the air in the lower part of the cave). During the 17th and 18th centuries, other gases were discovered, including hydrogen, oxygen, and nitrogen, and many of their properties were investigated. It was not until nearly the end of the 18th century, however, that these three gases were recognized as elements. When Lavoisier recognized that oxygen is an element, and that combustion is the process of combining with oxygen, the foundation of modern chemistry was laid.
Adapted from: Linus Pauling: General Chemistry. W.H. Freeman 1970, p.306.
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ON LANGUAGE REFORM IN CHEMISTRY
An argument can be made that nomenclature in science is as important as data, since nomenclature represents the prevailing conceptual organization of observations. Certainly, researchers in most sciences are constrained to adhere to the nomenclature rules of their field. Molecular biology is currently in a phase of general nomenclature chaos with respect to the naming of genes, but hopefully that phase will soon pass. Meanwhile, nomenclatures in other areas of biology are more organized, and 18th century plant taxonomy, in fact, served as a model for the nomenclature revolution in chemistry that occurred in conjunction with the "new chemistry" proposed by Antoine Lavoisier (1743-1794).
Lavoisier is often cited as the instigator of chemical nomenclature reform at the end of the 18th century, but four chemists were the prime movers of this reform: Lavoisier, Louis Guyton de Morveau (1737-1816), Claude Berthollet (1748-1822), and Antoine Fourcroy (1755-1809). Of the four, Guyton de Morveau, probably deserves more credit than the others, his efforts culminating in the publication of his /Method of Chemical Nomenclature/ in 1787 [*Note #1]. All the above chemists, however, collaborated in the nomenclature revision program, which quickly became accepted after the publication of Lavoisier's influential textbook /Elementary Treatise on Chemistry/ in 1789 [*Note #2].
Perhaps the most important general nomenclature revision was the adoption of a binomial scheme for naming compounds (influenced by the scheme then current in botany), but of specific importance was the renaming of "*dephlogisticated air" ("empyreal air; vital air) as "oxygen", and the renaming of "inflammable air" as "hydrogen", both new names based on prevailing knowledge of chemistry rather than on ambiguous attributes.
The following points are made by Bernadette Bensaude-Vincent (Nature 2001 410:415):
1) Guyton de Morveau initiated the French 18th century chemical nomenclature reform project and established a set of basic principles: a) nomenclature should reveal "the nature of things"; b) simple substances should have simple names evoking their most characteristic property; c) compound names should express the composition of chemical compounds; d) Greek etymologies should be used in preference to Latin.
2) Guyton de Morveau began his attempt to reform chemical nomenclature in 1782 and submitted his project to the Paris Academy of Sciences in January 1787. At the Academy, Guyton encountered a fierce debate concerning the existence of "phlogiston", the principle that was believed to explain combustion and reduction. Although most chemists at that time believed in phlogiston, Lavoisier's explanation of combustion was quite different. Guyton allied himself with Lavoisier, and with the help of Lavoisier, Berthollet, and Fourcroy, Guyton published a revised project in the spring of 1787, the revision making no mention of "phlogiston", but instead containing new words such as "oxygen", from Greek words meaning "acidifying principle", the new term stemming from Lavoisier's idea that all acids contained oxygen.
3) The author points out that the language reform of 1787-1789 was an integral part of the formation of the autonomous discipline of chemistry, contributed to the subordination of pharmacy to chemistry, and contributed to the redefinition of the chemical arts as applied chemistry. The new language forged by academic chemists separated many users of chemical substances from their own traditions. The new language ignored the physiological senses of chemists, banished all reference to geographical origins or the discovery of the substances, and imposed an analytical quantitative logic on chemical nomenclature.
4) Although the use of this logic proved to be a valuable method over time, the principles of the system were never strictly applied. Oxygen, for example, should have been renamed when Humphrey Davy (1778-1829) established that many acids do not contain oxygen. Colors and odors were restored after the discovery of chlorine and iodine, named from the Greek for "yellowish-green" and "violet", respectively. Bromine was named from the Greek word for "stink". Morphine was named after Morpheus, the god of dreams. Benzene was named after Styrax benzoin, a tree native to Sumatra and Java. Scandium, germanium, and polonium were named after political entities, and in the 20th century various new elements were named after historical scientific figures.
5) In general, the systematization imposed by the four 18th century reformer chemists in the name of rationality remained an ideal often contradicted by practice. At present, nomenclature rules in chemistry are under the control of a permanent commission, the International Union of Pure and Applied Chemistry (IUPAC).
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Notes:
Note #1: Louis Bernard Guyton de Morveau (1737-1816) was an interesting personage. His first profession was that of an attorney. In 1776, while still an attorney, he published the /Elements of Theoretical and Practical Chemistry/, a major attempt to quantify chemical affinities. In 1782, he gave up the law and devoted himself full-time to chemistry. In 1795, he founded the Ecole Polytechnique and taught there until 1805. Guyton was one of the first to conclude that iron and steel differ solely in their carbon content. He made improvements in the manufacture of gunpowder. He was the first to use chlorine and hydrochloric acid gas as disinfectants. He was one of the first balloonists, making two flights in 1784 and helping in the organization of the world's first air force, the Compagnie d'Aerostiers, whose reconnaissance balloonists assisted the French army in several battles during the Napoleonic wars.
Note #2: Concerning nomenclature in chemistry, the following passage appears in Lavoisier's /A General Introduction to Chemistry/ (1789):
"It is impossible to dissociate language from science or science from language, because every natural science always involves three things: the sequence of phenomena on which the science is based; the abstract concepts which call these phenomena to mind; and the words in which the concepts are expressed. To call forth a concept, a word is needed; to portray a phenomenon, a concept is needed. All three mirror one and same reality. Words are thus required to preserve and transmit ideas, so that it is clear that the advancement of a science and the improvement of its technical vocabulary go hand in hand. No matter how certain we are of the phenomena, no matter how adequately our concepts reflect them, we cannot help perpetuating wrong ideas unless we have a precise terminology in which to express ourselves."
Lavoisier, considered the father of modern chemistry, was no doubt the most eminent scientist to ever suffer death by the guillotine. In 1780, as a member of the French Academy of Sciences, Lavoisier was active in rejecting the application to the Academy of a certain physician Jean-Paul Marat (1743-1793). Marat apparently did not forget. During the French Revolution (1787-1799), Marat became a powerful revolutionary leader, and Marat was instrumental in bringing Lavoisier to trial for his investments in a much-hated company that collected taxes for the French government. Lavoisier was guillotined May 8, 1794 and buried in an unmarked grave. (Marat did not live to see this: Marat himself was assassinated in July 1793.)
dephlogisticated air: In this context, the term "phlogiston" refers to a 17th and 18th century chemical theory involving a hypothetical principle of fire. The idea was that every combustible substance is in part composed of phlogiston, with the phenomenon of burning caused by the liberation of phlogiston and the "dephlogistonated" substance remaining as ash or residue. The phlogiston theory was experimentally discredited by Lavoisier beginning in 1770, who showed that the newly discovered element oxygen was always involved in combustion.
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