Conduction in Solutions and Gase*, etc. 373 



K. Clausius,* of Zurich, the basis of a theory of electrolysis. 

 According to it, the electromotive force emanating from the 

 electrodes does not effect the dissociation of the electrolyte 

 into ions, since a degree of dissociation sufficient for the purpose 

 already exists in consequence of the perpetual mutability of the 

 molecules of the electrolyte. Clausius assumed that these ions 

 are in opposite electric conditions; the applied electric force 

 therefore causes a general drift of all the ions of one kind 

 towards the anode, and of all the ions of the other kind towards 

 the cathode. These opposite motions of the two kinds of ions 

 constitute the galvanic current in the liquid. 



The merits of the Williamson-Clausius hypothesis were not 

 fully recognized for many years ; but it became the foundation 

 of that theory of electrolysis which was generally accepted at 

 the end of the century. 



Meanwhile another aspect of electrolysis was receiving 

 attention. It had long been known that the passage of a 

 current through an electrolytic solution is attended not only 

 by the appearance of the products of decomposition at the 

 electrodes, but also by changes of relative strength in different 

 parts of the solution itself. Thus in the electrolysis of a solution 

 of copper sulphate, with copper electrodes, in which copper is 

 dissolved off the anode and deposited on the cathode, it is found 

 that the concentration of the solution diminishes near the 

 cathode, and increases near the anode. Some experiments on 

 the subject were made by Faradayf in 1835 ; and in 1844 it 

 was further investigated by Frederic Daniell and W. A. Miller, J 

 who explained it by asserting that the cation and anion have 

 not (as had previously been supposed) the same facility of 

 moving to their respective electrodes ; but that in many cases 

 the cation appears to move but little, while the transport is 

 effected chiefly by the anion. 



* Ann. d. Phys. ci (1857), p. 338 ; Phil. Mag. xv (1858), p. 94. 

 t Exper. Res. 525-53C. 



* Phil. Trans., 1844, p. 1. Cf. also Pouillet, Comptes Rendus xx (1845), 

 p. 1544. 



