Theory of Chemical Types : Electro-chemical Theory. 183 



the nomenclature of Lavoisier sees in it sulphate of potassa 

 and of chromium under the form of alum. 



Alum is a type ; all the alums are cast in the same mould ; 

 their form is what the theory of types would set forth espe- 

 cially ; that which essentially defines each of them. It ads 

 as an artist, who in seeing the statues consisting of different 

 materials cast from the same mould, will say to you, " Here 

 is the Venus of Milo in brass, in lead, in plaster." The art- 

 istic type strikes him before he dreams of the material, and he 

 will never think of saying that he is about to show you brass, 

 plaster, or bronze in the form of the Venus of Milo. 



An entire reform of the organic nomenclature and of some 

 parts of the mineral nomenclature, appears to me, then, both 

 urgent and possible. 



Electro-chemical theory.' We just now saw how the princi- 

 ple of dualism, introduced by the chemistry of Lavoisier in 

 the definition of every chemical combination, was favourable 

 to the conception of what is called the electro-chemical theory. 

 We have also understood how the theory of molecular types 

 swerves from this order of ideas, for it does not suppose two 

 antagonist elements present in the bodies, acting as would two 

 masses endowed with different electricities, and held in combi- 

 nations by the mutual action of these two electricities. 



Does a chemical combination constitute a simple edifice or 

 a double monument ? this is the question. In the theory of 

 types, the formulae combine, and are written without attending 

 to the reduction (dedoubler) of each body into two others. In 

 the electro-chemical theory they combine, and are written in 

 such a manner as always to paint to the mind these two prin- 

 cipal divisions of the edifice which they represent. 



This is the manner in which the theory of types has been 

 driven to separate itself from the electro-chemical theory, or 

 rather that in which this latter has been led to combat the 

 other from its first appearance. The question, however, is 

 given in the clearest way in the following letter from M. de la 

 Rive. The skilful Genevese philosopher, whose name will al- 

 ways be united with the history of electro-chemistry, wrote to 

 me on the 25th of October last (1839) : 



" I have read your researches on substitutions with very great 

 interest. They interested me the more as I have been occu- 

 pied for more than a year upon a rather large work on the 

 electro-chemical theories. I dare not, I must confess, go as far 

 as you ; and without believing in the theory of Berzelius such 

 as he has presented it, yet I cannot help thinking that there 

 is something well-founded in the table of the relative chemical 



