276 HISTORY OF CHEMISTRY. 



Antoine Laurent Lavoisier, an accomplished French chemist, had 

 pursued, with zeal and skill, researches such as those of Black, Caven- 

 dish, tand Priestley, which we have described above. In 1774, he 

 showed that, in the calcination of metals in air, the metal acquires as 

 much weight as the air loses. It might appear that this discovery at 

 once overturned the view which supposed the metal to be phlogiston 

 added to the calx. Lavoisier's contemporaries were, however, far from 

 allowing this; a greater mass of argument was needed to bring them 

 to this conclusion. Convincing proofs of the new opinion were, how- 

 ever, rapidly supplied. Thus, when Priestley had discovered dephlo- 

 gisticated air, in 1774, Lavoisier showed, in 1775, that fixed air con- 

 sisted of charcoal and the dephlogisticated or pure air; for the mercu- 

 rial calx which, heated by itself, gives out pure air, gives out, when 

 heated with charcoal, fixed air, 1 which has, therefore, since been called 

 carbonic acid gas. 



Again, Lavoisier showed that the atmospheric air consists of pure or 

 vital air, and of an unvital air, which he thence called azot. The vital 

 air he found to be the agent in combustion, acidification, calcination, 

 respiration ; all of these processes were analogous : all consisted in a 

 decomposition of the atmospheric air, and a fixation of the pure or 

 vital portion of it. 



But he thus arrived at the conclusion, that this pure air was added, 

 in all the cases in which, according to the received theory, phlogiston 

 was subtracted, and vice versa. He gave the name 2 of oxygen (principe 

 oxygene) to " the substance which thus unites itself with metals to form 

 their calces, and with combustible substances to form acids." 



A new theory was thus produced, which would account for all the 

 facts which the old one would explain, and had besides the evidence 

 of the balance in its favor. But there still remained some apparent 

 objections to be removed. In the action of dilute acids on metals, 

 inflammable air was produced. Whence came this element? The 

 discovery of the decomposition of water sufficiently answered this ques- 

 tion, and converted the objection into an argument on the side of the 

 theory : and thus the decomposition of water was, in fact, one of the 

 most critical events for the fortune of the Lavoisierian doctrine, and 

 one which, more than any other, decided chemists in its favor. In 

 succeeding years, Lavoisier showed the consistency of his theory with 



1 Mem. Ac. Pa* 1775. 2 Mem. Ac. Par. 1781. p. 448. 



