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him into association with farmer-general Paulze, whose daughter he married, and who went with him to the scaffold. In 1776 Turgot made him inspector-general of powder and saltpeter. In this capacity he made great improvements in the manufacture, so that, while he put a stop to forced official searches for saltpeter in the cellars of private houses, he quadrupled the product of the salt, and so increased the explosive force of gunpowder that the French brand became as much superior to the English as it had been inferior.

Lavoisier's great work consisted in the discovery of the true functions of oxygen and the nature of combustion; the determination of the relations of the solid, liquid, and gaseous states of matter; and in many other observations that embodied the germs of what have become since the leading principles of chemical science. Oxygen was detected at about the same time by Priestley, Scheele, and Lavoisier; but the phlogistic theory of combustion possessed the minds of chemists, and, although Eck de Suchbach and Jean Rey had already dimly discerned the truth, no one had paid any attention to their discoveries, and Lavoisier was working on what was to him, and substantially to the world, virgin ground. "Fixed air" and "combustible air" had been speculated upon, and "the air that is left after combustion" had attracted attention. But the phenomena of this kind, inconsistent as they were with the phlogistic theory, had not been sufficient to overthrow it. The first germ of Lavoisier's theory on these matters was embodied in a sealed packet which he deposited with the Academy in 1770. Recognizing that the calcination of metals could not take place without the access of air, and that the freer the access the more rapid the calcination, he "began to suspect," as he expresses himself, that some elastic fluid contained in the air was susceptible, under many circumstances, of fixing itself and combining with metals, and that to the addition of that substance were due calcination and the increase in weight of metals converted into calxes. From this thought came, after much groping with erroneous conclusions, the idea that air is a compound containing a vital part and another part, and that it is the vital part that is absorbed. The behavior of charcoal when burning in oxygen pointed to the nature of that substance and to the true theory of combustion. This new vital substance, which, uniting with metals, formed calxes, and with other substances generated acids, he called oxygen or the acid-producer; the air that was left after combustion was azote, or lifeless. The inflammable air which, combining with oxygen, was found to form water, was called hydrogen. Upon these facts, and with a few other names of known substances, Lavoisier constructed the system of chemical nomenclature which, after having undergone many modifications to conform to