1904.] on Development of the Theory of Electrolytic Dissociation. 555 



cules turn round under the influence of the electric force, so that 

 we get the scheme 3 and a new decomposition can take place. This 

 represents the Grotthuss' scheme, that supposes continuous decom- 

 positions and recombinations of the salt molecules. 



As such exchanges of ions between the molecules take place 

 even under the influence of the weakest electromotive forces, Clausius 

 concluded that they must also take place if there is no electric force, 

 i.e. no current at all. In favour of his hypothesis he pointed to 

 the fact that Williamson, as far back as 1852, in his epoch-making 

 theory of the formation of ethers, assumed an analogous exchange of 

 the constituents of the molecules. At this exchange of ions it might 

 sometimes, though extremely rarely, happen that an ion becomes free 

 in the solution for a short time ; at least such a conception would be 



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j:!- 



FiG. 3. 



in good agreement with the mechanical theory of heat, as it was 

 developed by Kronig, Maxwell, Clausius and others at that time. 



In the meantime, Bouty, and particularly Kohlrausch worked out 

 the methods of determining the electric conductivity of salt solutions. 

 In 1884 I published a memoir on this subject. I had found that if 

 one dilutes a solution — e.g. of zinc sulphate — its conductivity per 

 molecule, or what is called its molecular conductivity, increases not 

 infinitely, but only to a certain limit. We may figure to ourselves an 

 experiment performed in the following manner (Fig. 3). In a trough 

 with parallel walls there are placed close to two opposite sides two 

 plates of amalgamated zinc, E E^. On the horizontal bottom of the 

 vessel there is placed a layer of solution of zinc-sulphate that reaches 

 the level 1. The conductivity may be Jc-^. After this has been measured 

 we pour in so much water, that after stirring the solution the level 

 reaches 2, which lies as much above 1 as this lies above the bottom. 



Vol. XYII. (Xo. 98.) 2 p 



