Lavoisier, Antoine Laurent (äNtwän´ lōräN´ lävwäzyā´), 1743-94, French chemist and physicist, a founder of modern chemistry. He studied under eminent men of his day, won early recognition, and was admitted to the Academy of Sciences in 1768. Much of his work was the result of extending and coordinating the research of others; his concepts were largely evolved through his superior ability to organize and interpret and were substantiated by his own experiments. He was one of the first to introduce effective quantitative methods in the study of chemical reactions. He explained combustion and thereby discredited the phlogiston theory. He also described clearly the role of oxygen in the respiration of both animals and plants. His classification of substances is the basis of the modern distinction between chemical elements and compounds and of the system of chemical nomenclature. He also conducted experiments to establish the composition of water and of many organic compounds. Lavoisier worked as well to improve economic and social conditions in France, holding various government posts. He was appointed director of the gunpowder commission (1775), member of the committee on agriculture (1785), director of the Academy of Sciences (1785), member of the commission on weights and measures (1790), and commissioner of the treasury (1791). As one of the farmers general, however, charged with the collection of taxes, he was guillotined during the Reign of Terror. His works include Traité élémentaire de chimie (1789) and the posthumously published Mémoires de chimie (1805).