In a memoir presented to the Academy in 1777, but not pub lished till 1782, he assigned to dephlogisticated air the name oxy gen, or "acid-producer," on the erroneous supposition that all acids were formed by its union with a simple, usually non-metallic, body. Combustion was explained by Lavoisier as due, not to the liberation of the hypothetical "phlogiston," hut to the result of the combination of the burning substance with oxygen. On June 25, 1783, in conjunction with Laplace, he announced to the Acad emy that water was the product formed by the combination of hydrogen and oxygen; by that time, however, he had been antici pated by Cavendish. From his knowledge of the composition of water Lavoisier was led to the beginnings of quantitative organic analysis. He burnt alcohol, and other combustible organic com pounds, in oxygen and from the weight of water and carbon dioxide produced calculated their composition.
Up to about this time Lavoisier's work, mainly quantitative in character, had appealed most strongly to physicists, but it now began to win conviction from chemists also. C. L. Berthollet, L. B. Guyton de Morveau and A. F. Fourcroy, his collaborators in the reformed system of chemical terminology set forth in 1787 in the Methode de nomenclature chimique, were among the ear liest French converts to the new theory of combustion ; they were followed by M. H. Klaproth and the German Academy, and by most English chemists except Cavendish, who rather suspended his judgment, and Priestley, who clung to the old ideas. The spread of Lavoisier's doctrines was greatly facilitated by the de fined and logical form in which he presented them in his Traite elementaire de chimie (presente dans un ordre nouveau et d'apres les decouvertes modernes) (1789), and eventually they were adopted universally. The list of simple substances (elements), which could not be further decomposed by any known process of analysis, contained in the first volume of this work, includes "light" and "caloric" with oxygen, azote and hydrogen. Under the head of "oxidable or acidifiable" substances, the combination of which with oxygen yielded acids, were placed sulphur, phos phorus, carbon, and the muriatic, fluoric and boracic radicles. The metals, which by combination with oxygen became oxides, were antimony, silver, arsenic, bismuth, cobalt, copper, tin, iron man ganese, mercury, molybdenum, nickel, gold, platinum, lead, tung sten and zinc ; and the "simple earthy salifiable substances" were lime, baryta, magnesia, alumina and silica. The simple nature of
the alkalies he considered so doubtful that he did not class them as elements. It is to Lavoisier that we owe to a great extent the modern concept of an element as against the old Greek idea.
In addition to his purely chemical work, Lavoisier, mostly in conjunction with Laplace, devoted considerable attention to phys ical problems, especially those connected with heat. The two car ried out some of the earliest thermochemical investigations, de vised apparatus for measuring linear and cubical expansions, and employed a modification of Joseph Black's ice calorimeter in a series of determinations of specific heats (see CALORIMETRY). Regarding heat as a peculiar kind of imponderable matter, La voisier held that the three states of aggregation—solid, liquid and gas—were modes of matter, each depending on the amount of tnatiere de feu with which the substances concerned were asso ciated. He also worked at fermentation, respiration and animal heat, looking upon the processes concerned as essentially chemical in nature. A paper discovered many years after his death showed that he had anticipated later thinkers in explaining the cyclical process of animal and vegetable life.