CH. xxvii. LAVOISIER'S EXPERIMENTS. 235 



Antoine Laurent Lavoisier was born in Paris in 1743. 

 His father, who was a wealthy merchant, gave him a 

 splendid education, and when he was still quite young the 

 new discoveries which were being made in chemistry tempted 

 him to learn that science. At twenty-one years of age he 

 received a gold medal from the Academic des Sciences for 

 a very elaborate and learned essay on the best way of light- 

 ing the streets of Paris. At five-and-twenty he was elected 

 a member of the Academic, and from that time he deter- 

 mined to devote his life to chemistry. 



As early as 1770 Lavoisier had begun to suspect that 

 the famous theory of phlogiston was false. His chief reason 

 for thinking this was that he found, as Geber had done more 

 than 900 years before (see p. 44), that when metals are 

 heated so that they turn into powder, the powder weighs 

 more than the original metal did before it was heated. 

 Moreover, he also found that the air which remained behind 

 in the vessel in which the metal had been heated had lost 

 exactly as much weight as the metal had gained. So it seemed 

 to him clear that the metal must have taken something/h?/;* 

 the air instead of giving anything to it 



For eight years Lavoisier worked incessantly at this 

 problem. He heated many metals, such as iron, lead, tin, 

 etc., and other substances such as sulphur and phosphorus, 

 and in every case, if he collected all that remained, he found 

 it heavier than before. But there was one point in which he 

 could not succeed ; he could not make the metals give back 

 again what they had taken from the air, so that he might 

 examine it At last, in 1778, it occurred to him that 

 Priestley had separated mercuric oxide into two substances ; 



discovered by Priestley, Scheele, and Cavendish, were merely the raw 

 material out of which Lavoisier constructed a consistent and comprehen 

 sive theory.' Inaugural Lecture, Edinburgh, 1869. 



