84 Mr. J. Brown on the Theory of 



dissociated part-molecules in the electrolyte are normally 

 engaged in ousting other part-molecules from their partners 

 by a process of exchange which, when directed by the attrac- 

 tion of the positive and negative poles, constitutes electro- 

 lysis; the dissociated part-molecules finally becoming attracted 

 to their respective poles and evolved there in the free state "*. 



It is evident, however, that by this process the original 

 number of dissociated part-molecules is not increased, and 

 therefore must soon become exhausted at the electrodes by 

 the action described, after which conduction would cease. 

 Yet it is evidently necessary for continuous conduction that a 

 steady average proportion of dissociated part-molecules be 

 supplied. 



A process which would provide for at least some fresh 

 dissociation of whole molecules is described in the third 

 paragraph of § 7 as one that may occur, but does not seem to 

 be recognized as a necessity. It is assumed that in the 

 course of the heat-vibrations among the molecules the nega- 

 tive part of one whole molecule may come so close to the 

 positive of another as to combine with it, leaving the former 

 partners of each free. (It would seem more likely that if two 

 partners combined, the other two would combine also, and 

 w^ould not be left free to move apart against the attraction of 

 their supposed electric charges.) 



Granting, however, for the moment that dissociation of this 

 kind may occur, and that thereby a certain steady average 

 proportion of molecules in the liquid is kept dissociated, and 

 that these are supposed to be led away in opposite directions 

 by the electric force acting on their supposed electric charges. 

 Now r , if we consider any given volume of the electrolyte, this 

 abduction of molecules would destroy the balance between the 

 associated and dissociated molecules, and therefore would 

 lead to fresh dissociation in order to restore it. This disso- 

 ciation requires a considerable amount of energy, whereas the 

 deportation of the molecules involves a very small amount of 

 electric work done ; thus we should have the heat of the 

 fluid used up to produce energy of a mechanically utilizable 

 type, in contradiction to the law of entropy and also in 

 disagreement with experimental observation. 



* It is, of course, very well known that Faraday objected to calling- 

 substances " electropositive or electronegative according as they go under 

 the supposed influence of a direct attraction to the positive or negative 

 pole," and considered these terms " much too significant " (Exp. Res. i. 

 p. 197). 



^ Hittorf also states as a conclusion from his research on the migration 

 of ions, " Es ist ganz falsch den Polen besondere Anziehungs- oder Abstos- 

 sungskraite zu ertheilen " (Pogg. Ann, ciii. p. 20, 1858). 



