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Lavoisier, Antoine Laurent

chemical chemistry tax combustion

[lavwazyay] (1743–94) French chemist and social reformer; creator of the Chemical Revolution and victim of the French Revolution.

Lavoisier’s father was a prosperous lawyer in Paris and the boy studied law after leaving school. However, he had been interested in science at school and later a family friend, , the geologist, took him on field trips. Lavoisier worked on the first geological map of France; this work, and his competition essay on a method of street-lighting, was so good that he was elected to the Royal Academy of Sciences in 1768, when he was only 25. In the same year he bought a part-share as a ‘tax-farmer’, to give him an income while he followed his new interest, chemistry. The tax-collecting company had leased from the Government the right to collect some indirect taxes for 6 years. The investment proved reasonable; he worked hard on company business; and at 28 he met and married Marie Anne Paulze, the 14-year-old daughter of a fellow tax-farmer (see next entry). She became the expert assistant in his chemical work. His involvement in the tax-farm was to prove unfortunate.

Solar furnace built for the Académie des Sciences in 1774. The 4- lens A was made of two pieces of glass, each moulded as part of a 16-sphere: the interior was filled with ethanol. A similar furnace was used by Lavoisier in 1772 in his experiments on heating metals and their oxides, and diamond, without flame or access to air. The device is early in state-supported Big Science, the 18th-c equivalent of a modern particle accelerator.

Lavoisier worked on a scheme for improving the water supply to Paris and on methods of purifying water. He showed in 1770 that water cannot be converted into earth, as was then widely believed. In this, as in all his work, he used the law of conservation of matter: that, in chemical operations, matter is not created or destroyed. He went on to show that air is a mixture of two gases: oxygen, which combines with reactive metals on heating and which supports combustion and respiration; and the unreactive nitrogen. He found that metals combine with oxygen to give oxides which are basic (‘alkaline’), whereas the non-metals (S,P,C) give acidic oxides. In this work he used the sort of logic he admired in studies on lime; and he was helped by information from ; but he used his own work, and that of others, to form a general theory of combustion, oxidation and the composition of the air, in an original way. His new theory soon displaced ‘phlogiston’ from most chemists’ minds and directed chemistry into new and valuable paths. He showed that water was a compound of hydrogen and oxygen; work on this was skilful, but it was Lavoisier who first explained the results. (Similarly, and Priestley had made oxygen before him, but failed to understand its significance.)

From 1776 he lived and worked happily at the Royal Arsenal, in effective charge of gunpowder production and research. It was there, with as Lavoisier’s co-worker, that Black’s early work on calorimetry was extended; an ingenious ice calorimeter was made for this, and heats of combustion and respiration were measured; this was the beginning of thermochemistry and also showed that animal respiration is essentially a slow combustion process. (A young assistant to Lavoisier at the Arsenal, E I du Pont (1771–1834), emigrated to America and in 1802 began making gunpowder on the banks of the Brandywine River in Delaware. The venture prospered and founded a major US chemical industry.) In 1787, with three other French chemists, Lavoisier introduced the method of naming chemical compounds which has been used ever since. His main contributions to chemistry were elegantly set out in his Elementary Treatise on Chemistry (1789), with fine plates by his wife. In it he gave his definition of a chemical element, as ‘the last point which analysis can reach’; this was view, but Lavoisier used it experimentally  and gave a working list of elements. The book had enormous influence on chemistry, comparable with Principia in physics a century earlier.

Lavoisier had remarkable energy: from 1778 he ran an experimental farm near Blois to improve the poor level of French agriculture; he developed schemes for improving public education, equitable taxation, savings banks, old age insurance and other welfare schemes. His liberal and generous views found too few imitators, however, and by 1789 revolution had begun. All might have gone well for Lavoisier for, although the tax-collecting firm was a natural target, its affairs were in good order and charges against the tax-farmers could be refuted. But revolution followed its usual pattern of moving to extremism, and Marat, a leading figure in the Terror, had early in his career pursued scientific ambitions–his worthless pamphlet Physical Researches on Fire had been condemned by Lavoisier. A new charge of ‘counter-revolutionary activity’ was speedily contrived, which ensured a guilty verdict, and France’s greatest scientist was guillotined the next day.

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