Antoine Lavoisier

It is generally accepted that Lavoisier's great accomplishments in chemistry stem largely from his changing the science from a qualitative to a quantitative one. Lavoisier is most noted for his discovery of the role oxygen plays in combustion. He recognized and named oxygen (1778) and hydrogen (1783), and opposed the phlogiston theory. Lavoisier helped construct the metric system, wrote the first extensive list of elements, and helped to reform chemical nomenclature. He predicted the existence of silicon (1787) and was also the first to establish that sulfur was an element (1777) rather than a compound. He discovered that, although matter may change its form or shape, its mass always remains the same.

The son of an attorney at the Parlement of Paris, he inherited a large fortune at the age of five upon the death of his mother. Lavoisier began his schooling at the Collège des Quatre-Nations, University of Paris (also known as the Collège Mazarin) in Paris in 1754 at the age of 11. In his last two years (1760–1761) at the school, his scientific interests were aroused, and he studied chemistry, botany, astronomy, and mathematics. In the philosophy class he came under the tutelage of Abbé Nicolas Louis de Lacaille, a distinguished mathematician and observational astronomer who imbued the young Lavoisier with an interest in meteorological observation, an enthusiasm which never left him. Lavoisier entered the school of law, where he received a bachelor's degree in 1763 and a licentiate in 1764. Lavoisier received a law degree and was admitted to the bar, but never practiced as a lawyer. However, he continued his scientific education in his spare time.

In collaboration with Guettard, Lavoisier worked on a geological survey of Alsace-Lorraine in June 1767. In 1764 he read his first paper to the French Academy of Sciences, France's most elite scientific society, on the chemical and physical properties of gypsum (hydrated calcium sulfate), and in 1766 he was awarded a gold medal by the King for an essay on the problems of urban street lighting. In 1768 Lavoisier received a provisional appointment to the Academy of Sciences.[12] In 1769, he worked on the first geological map of France.

Lavoisier consolidated his social and economic position when, in 1771 at age 28, he married Marie-Anne Pierrette Paulze, the 13-year-old daughter of a senior member of the Ferme générale.[4] She was to play an important part in Lavoisier's scientific career—notably, she translated English documents for him, including Richard Kirwan's Essay on Phlogiston and Joseph Priestley's research. In addition, she assisted him in the laboratory and created many sketches and carved engravings of the laboratory instruments used by Lavoisier and his colleagues for their scientific works. Madame Lavoisier edited and published Antoine's memoirs (whether any English translations of those memoirs have survived is unknown as of today) and hosted parties at which eminent scientists discussed ideas and problems related to chemistry.

Oxygen theory of combustion

During late 1772 Lavoisier turned his attention to the phenomenon of combustion, the topic on which he was to make his most significant contribution to science. He reported the results of his first experiments on combustion in a note to the Academy on 20 October, in which he reported that when phosphorus burned, it combined with a large quantity of air to produce acid spirit of phosphorus, and that the phosphorus increased in weight on burning. In a second sealed note deposited with the Academy a few weeks later (1 November) Lavoisier extended his observations and conclusions to the burning of sulfur and went on to add that "what is observed in the combustion of sulfur and phosphorus may well take place in the case of all substances that gain in weight by combustion and calcination: and I am persuaded that the increase in weight of metallic calces is due to the same cause."

Joseph Black's "fixed air"

During 1773 Lavoisier determined to review thoroughly the literature on air, particularly "fixed air," and to repeat many of the experiments of other workers in the field. He published an account of this review in 1774 in a book entitled Opuscules physiques et chimiques (Physical and Chemical Essays). In the course of this review he made his first full study of the work of Joseph Black, the Scottish chemist who had carried out a series of classic quantitative experiments on the mild and caustic alkalies. Black had shown that the difference between a mild alkali, for example, chalk (CaCO3), and the caustic form, for example, quicklime (CaO), lay in the fact that the former contained "fixed air," not common air fixed in the chalk, but a distinct chemical species, now understood to be carbon dioxide (CO2), which was a constituent of the atmosphere. Lavoisier recognized that Black's fixed air was identical with the air evolved when metal calces were reduced with charcoal and even suggested that the air which combined with metals on calcination and increased the weight might be Black's fixed air, that is, CO2.

Joseph Priestley

In the spring of 1774 Lavoisier carried out experiments on the calcination of tin and lead in sealed vessels, the results of which conclusively confirmed that the increase in weight of metals in combustion was due to combination with air. But the question remained about whether it was combination with common atmospheric air or with only a part of atmospheric air. In October the English chemist Joseph Priestley visited Paris, where he met Lavoisier and told him of the air which he had produced by heating the red calx of mercury with a burning glass and which had supported combustion with extreme vigor. Priestley at this time was unsure of the nature of this gas, but he felt that it was an especially pure form of common air. Lavoisier carried out his own researches on this peculiar substance. The result was his memoirOn the Nature of the Principle Which Combines with Metals during Their Calcination and Increases Their Weight, read to the Academy on 26 April 1775 (commonly referred to as the Easter Memoir). In the original memoir Lavoisier showed that the mercury calx was a true metallic calx in that it could be reduced wit charcoal, giving off Black's fixed air in the process. When reduced without charcoal, it gave off an air which supported respiration and combustion in an enhanced way. He concluded that this was just a pure form of common air, and that it was the air itself "undivided, without alteration, without decomposition" which combined with metals on calcination.

Pioneer of stoichiometry

Lavoisier's researches included some of the first truly quantitative chemical experiments. He carefully weighed the reactants and products of a chemical reaction in a sealed glass vessel so that no gases could escape, which was a crucial step in the advancement of chemistry. In 1774, he showed that, although matter can change its state in a chemical reaction, the total mass of matter is the same at the end as at the beginning of every chemical change. Thus, for instance, if a piece of wood is burned to ashes, the total mass remains unchanged if gaseous reactants and products are included. Lavoisier's experiments supported the law of conservation of mass. In France it is taught as Lavoisier's Law and is paraphrased from a statement in his Traité Élémentaire de Chimie: "Nothing is lost, nothing is created, everything is transformed." Mikhail Lomonosov (1711–1765) had previously expressed similar ideas in 1748 and proved them in experiments; others whose ideas pre-date the work of Lavoisier include Jean Rey (1583–1645), Joseph Black (1728–1799), and Henry Cavendish (1731–1810).

Chemical nomenclature

Lavoisier, together with Louis-Bernard Guyton de Morveau, Claude-Louis Berthollet, and Antoine François de Fourcroy, submitted a new program for the reforms o chemical nomenclature to the Academy in 1787, for there was virtually no rational system of chemical nomenclature at this time. This work, titled Méthode de nomenclature chimique (Method of Chemical Nomenclature, 1787), introduced a new system which was tied inextricably to Lavoisier's new oxygen theory of chemistry. The Classical elements of earth, air, fire, and water were discarded, and instead some 55 substances which could not be decomposed into simpler substances by any known chemical means were provisionally listed as elements. The elements included light; caloric (matter of heat); the principles of oxygen, hydrogen, and azote (nitrogen); carbon; sulfur; phosphorus; the yet unknown "radicals" of muriatic acid (hydrochloric acid), boric acid, and "fluoric" acid; 17 metals; 5 earths (mainly oxides of yet unknown metals such as magnesia, baria, and strontia); three alkalies (potash, soda, and ammonia); and the "radicals" of 19 organic acids. The acids, regarded in the new system as compounds of various elements with oxygen, were given names which indicated the element involved together with the degree of oxygenation of that element, for example sulfuric and sulfurous acids, phosphoric and phosphorous acids, nitric and nitrous acids, the "ic" termination indicating acids with a higher proportion of oxygen than those with the "ous" ending. Similarly, salts of the "ic" acids were given the terminal letters "ate," as in copper sulfate, whereas the salts of the "ous" acids terminated with the suffix "ite," as in copper sulfite. The total effect of the new nomenclature can be gauged by comparing the new name "copper sulfate" with the old term "vitriol of Venus." Lavoisier's new nomenclature spread throughout Europe and to the United States and became common use in the field of chemistry. This marked the beginning of the anti-phlogistic approach to the field.

Elementary Treatise of Chemistry

Lavoisier employed the new nomenclature in his Traité élémentaire de chimie (Elementary Treatise on Chemistry), published in 1789. This work represents the synthesis of Lavoisier's contribution to chemistry and can be considered the first modern textbook on the subject. The core of the work was the oxygen theory, and the work became a most effective vehicle for the transmission of the new doctrines. It presented a unified view of new theories of chemistry, contained a clear statement of the law of conservation of mass, and denied the existence of phlogiston. This text clarified the concept of an element as a substance that could not be broken down by any known method of chemical analysis, and presented Lavoisier's theory of the formation of chemical compounds from elements. It remains a classic in the history of science. While many leading chemists of the time refused to accept Lavoisier's new ideas, demand for Traité élémentaire as a textbook in Edinburgh was sufficient to merit translation into English within about a year of its French publication.mIn any event, themTraité élémentairem was sufficiently sound to convince the next generation.