THE ATOMIC VIEW OF NATURE. 



391 



determinations. That rule is indeed the foundation of all 

 work in the laboratory, the principle which decides the 

 degree of accuracy attained in every analysis, and which 

 not infrequently is the only method of determining the 

 presence of some undiscovered constituent. 1 Not long 



1 The revolution in chemistry at 

 the end of the last century manifests 

 itself in nothing more than in the 

 various distinct problems, corre- 

 sponding to different courses of 

 scientific thought and different in- 

 terests, which have guided chemical 

 research since that time. The first 

 definite object was the search after 

 the real elements, the attempt to 

 decompose the existing substances 

 of nature into their ultimate con- 

 stituents. This interesting occu- 

 pation somewhat pushed into the 

 background the theoretical investi- 

 gations regarding the forms of the 

 combinations of the various ele- 

 ments into compounds, still more 

 the study of chemical affinity. A 

 second definite object was the de- 

 velopment of the theory of combus- 

 tion which Lavoisier propounded, 

 and the confirmation or refutation 

 of the idea according to which 

 oxygen occupied almost as import- 

 ant a position in chemical reactions 

 as phlogiston had done before. A 

 third definiteobject was the develop- 

 ment of analytical chemistry, the 

 systematic and methodical use of 

 the balance. So far as the first 

 branch of this pursuit was con- 

 cerned, Lavoisier's catalogue of the 

 elements was still very incomplete ; 

 it contained thirty-three members, 

 including light and heat, and 

 twenty-three of the substances 

 which now figure in the list of the 

 seventy elements enumerated in the 

 text- books ; the alkalies and earths 

 were still considered to be simple 

 bodies. A great addition to our 

 knowledge in this department came 



through Davy's decomposition of 

 soda and potash. And after his 

 proof of the elementary nature of 

 chlorine the oxygen theory of La- 

 voisier had also to be greatly modi- 

 fied. " Through a series of most 

 important investigations, he rose in 

 the beginning of this century to 

 such eminence, that he was then 

 considered to be the first represen- 

 tative of chemical science. With 

 great experimental ability he com- 

 bined a singular freedom from all 

 the theoretical doctrines which were 

 recognised in his age" (Kopp, ' Ent- 

 wickelung der Chemie,' p. 451). In 

 this he resembled Dalton and Fara- 

 day and other natural philosophers 

 in this country, on whom theoretical 

 notions formed in the Continental 

 schools had little or no influence. 

 Qualitative analysis was less indebt- 

 ed to Lavoisier than other branches 

 of the science were. In fact, it was 

 more at home in Sweden and Ger- 

 many, where the interests of miner- 

 alogy and metallurgy promoted it. 

 Bergmann and Scheele in Sweden, 

 Klaproth in Berlin, were the fore- 

 runners of Berzelius and of the 

 Berlin school of analysts. In this 

 country Black and especially Caven- 

 dish had carried out some important 

 quantitative determinations, the ac- 

 curacy of which seems very far be- 

 hind modern standards (see Kopp, 

 'Qeschichte der Chemie,' vol. ii. p. 

 70, &c., 1844). It was the introduc- 

 tion of the notion of chemical equi- 

 valence, a term used already by 

 Cavendish, which furnished the 

 ultimate test for accuracy and re- 

 volutionised quantitative analysis. 



