Lavoisier , Antoine Laurent

(1743–1794) French chemist

Lavoisier is regarded as the founder of modern chemistry. Born in Paris, he studied both law and science, but after graduating concentrated his attention on science. He invested his money in a private tax-collecting company, the Ferme Générale, and thereby became rich enough to build a large and well-equipped laboratory. He then proceeded to study combustion.

During the 18th century combustible matter was thought to contain a substance called phlogiston, which was released when combustion took place. This theory, which was developed by Georg Stahl, had one obvious flaw; substances frequently increase in weight as a result of combustion. Lavoisier performed a number of experiments in which he burned phosphorus, lead, and other elements in closed containers; he noted that the weight of the container and its contents did not increase though that of the solid did. In 1772 he recorded his observations that phosphorus and sulfur burn with a gain in weight caused by their combination with air. In 1774 he discovered that when a calx (oxide) was heated with charcoal (carbon) the gas produced was the ‘fixed air’ found by Joseph Black. This suggested that the element was combining with air. Soon after this, Lavoisier was visited by Joseph Priestley in Paris. Priestley had recently discovered that mercury(II) oxide gives off a gas when heated, leaving behind mercury. Priestley called the gas ‘dephlogisticated air’. Lavoisier repeated Priestley's experiments and, by 1778, had convinced himself of the existence in the air of a gas that combines with substances during combustion and is the same gas as that given off by heating mercury(II) oxide. Lavoisier named the gas ‘oxygine’ from the Greek ‘acid producing’ – he held the erroneous belief that all acids contain oxygen. He further recognized the existence of a second, inert, gas in the air – ‘azote’ (named from the Greek ‘no life’ and later renamed nitrogen). In 1783 he explained the formation of water from hydrogen and oxygen, work that led to a controversy involving Henry Cavendish. Lavoisier then went on to study respiration and deduced that oxygen is essential to animal life.

In 1783 he collaborated with Claude Berthollet, Antoine François de Fourcroy and L.B. Guyton de Morveau in publishing Méthode de nomenclature chimique (System of Chemical Nomanclature), which proposed new names for the elements. In 1789 he published Traité élémentaire de chimie (Elementary Treatise on Chemistry) – an influential work summarizing his ideas and stating the law of conservation of mass. The book also contained a list of the known elements, although this included light and heat (caloric).

In 1771 Lavoisier married the attractive and talented fourteen-year-old Marie Anne Pierrette Paulze (1758–1836), the daughter of a wealthy tax-farmer. Marie Lavoisier had studied under the painter David and had learned English and Latin. Her skills as a draftswoman are evident in the thirteen pages of copperplate illustrations accompanying her husband's Traité and signed “Paulze Lavoisier sculpsit”. She translated a number of important texts including Richard Kirwan's Essay on Phlogiston (1784). It is also clear that Madame Lavoisier actually worked with her husband in his laboratory and there is a celebrated painting by David dating from about 1788 showing them so occupied. The nature of the collaboration, however, remains unclear. Her last service for her husband was to collect and publish his Mémoires de chemie (1803, 2 vols.; Memoirs of Chemistry).

Lavoisier became, in 1775, director of the government powder mills and as such considerably improved the production of gunpowder. He also made contributions to agriculture and demonstrated the advantages of scientific farming on a model farm at Fréchines. He was a member of the commission, appointed in 1790, that eventually led to the adoption of the metric system in France.

Tragically Lavoisier's involvement with the tax-gathering company was to prove his downfall. In the 1790s France was in the middle of a protracted revolution and, in 1794, Paris was ruled by a radical group of republicans – the Jacobins – who ruthlessly executed thousands of alleged opponents of the revolution. Among these were included the tax gatherers and Lavoisier, despite his work for the state, was tried as a farmer of taxes, found guilty, and guillotined in Paris.