BEGINNINGS OF MODERN CHEMISTRY 



gas so " elastic" as to pass through the pores of a ves- 

 sel. He demonstrated the fallaciousness of both these 

 theories in 1768-1769 by elaborate experiments, a sin- 

 gle investigation of this series occupying one hundred 

 and one days. 



In 1771 he gave the first blow to the phlogiston 

 theory by his experiments on the calcination of metals. 

 It will be recalled that one basis for the belief in phlogis- 

 ton was the fact that when a metal was calcined it was 

 converted into an ash, giving up its "phlogiston " in 

 the process. To restore the metal, it was necessary to 

 add some substance such as wheat or charcoal to the 

 ash. Lavoisier, in examining this process of restora- 

 tion, found that there was always evolved a great 

 quantity of " air," which he supposed to be " fixed air" 

 or carbonic acid the same that escapes in efferves- 

 cence of alkalies and calcareous earths, and in the fer- 

 mentation of liquors. He then examined the process 

 of calcination, whereby the phlogiston of the metal 

 was supposed to have been drawn off. But far from 

 finding that phlogiston or any other substance had 

 been driven off, he found that something had been 

 taken on: that the metal "absorbed air," and that the 

 increased weight of the metal corresponded to the 

 amount of air "absorbed." Meanwhile he was within 

 grasp of two great discoveries, that of oxygen and of 

 the composition of the air, which Priestley made some 

 two years later. 



The next important inquiry of this great French- 

 man was as to the composition of diamonds. With the 

 great lens of Tschirnhausen belonging to the Academy 

 he succeeded in burning up several diamonds, regardless 



