I7 2 HISTORY OF CHEMISTRY. [LECTURE IX. 



Perhaps Berzelius did not notice that he had thus conceded 

 the chief point in the theory of substitution which, a few years 

 before, he had vigorously contested. Chlorine could replace 

 the hydrogen of the " copula," and the constitution of the 

 compound was not essentially altered thereby. Berzelius now 

 wrote : 



C 2 O 8 + C 2 C1 3 Chloracetic acid. 



C 2 O 3 + C 2 H 3 Acetic acid. 



Was a fundamental principle of the electro-chemical theory 

 not violated by this concession? I think it was. It was 

 now necessary to assume either that forces different from the 

 electrical forces were present in the copula, or that the electri- 

 cal properties of the elements are altered in the compound ; 

 and both of these assumptions were much at variance with the 

 former ideas of Berzelius. 



The substitution theory had thus come off victorious. 

 Berzelius, it is true, never admitted his defeat, but, as a matter 

 of fact, he had given in. The electro- chemical theory was 

 now abandoned. In its last throes it had produced the idea of 

 copulae : had these latter any vitality ? At first it did not seem 

 so ; they were looked upon as the idle invention of a wearied 

 intellect. With this I partly agree ; but they still possessed a 

 spark of life, otherwise they would not have been capable of 

 development, and it would not have been possible even for 

 a man like Kolbe to advance them to what they afterwards 

 became. 



This subject will be dealt with in a subsequent lecture. 



