1 62 HISTORY OF CHEMISTRY. [LECTURE IX. 



definitions assumed a much more fixed and decided form. The 

 distinction between the basicity and the atomicity of an acid 

 was learned at a still later date, and rules were formulated 

 whereby these also can be ascertained numerically. But these 

 developments fall into a period which is too far removed from 

 the one now under consideration for us to be able to discuss 

 them here at present. 



It will easily be understood that Berzelius could not share 

 Liebig's opinions. To recognise them would have been to 

 abandon dualism, the basis of his own theories. It is true that 

 the new way of looking at substances was not purely unitary ; 

 the acids were supposed to consist of radical and hydrogen, 

 and the salts, of radical and metal, so that there still existed 

 a division into two parts ; but this was in a sense in which 

 Berzelius could not admit it. The mode of salt forma- 

 tion, as Liebig conceived it, must especially have been in 

 opposition to his views. There were no longer tw r o com- 

 pounds of the first order an electro-positive and an electro- 

 negative constituent which united ; the formation of salts 

 consisted, instead, in the replacement of hydrogen. How could 

 this be reconciled w r ith. the electro-chemical theory, in accord- 

 ance with which compounds are only formed by the union of 

 atoms one with another? Hence we find Berzelius also pro- 

 testing 24 against the theory of hydrogen acids, if I may thus 

 designate Dulong's ideas. His reasons w r efe not sufficient, 

 however, to dissuade the greater number of chemists from 

 adopting this theory, and on this account I shall not enter more 

 minutely into the matter, but shall again turn to the facts which 

 were to lead to a unitary system. I refer to the phenomena of 

 substitution, or to the replaceability of hydrogen by electro- 

 negative elements. 



Besides Dumas and Laurent, Regnault and Malaguti were 

 especially engaged in the investigation of this subject. The 

 results obtained by these chemists the theories of Laurent, as 

 well as Liebig's views concerning acids had not been without 



24 Berzelius, Jahresbericht 1839, 264 ; Annalen. 31, I. 



