Electrolytic Conduction of Glausius. 85 



On the other hand, if the work done bj the current, in 

 separating from any electrolyte certain substances, is the 

 equivalent of the heat evolved by the recombination of those 

 substances, it seems simpler to assume that the work is 

 directly applied to produce decomposition at the electrodes. 



The hypothesis of molecular interchange as proposed by 

 Williamson to explain the process of etherification is quoted 

 by Clausius in §10 in support of his theory; but Williamson's 

 process was purely one of molecular interchange between the 

 partners of whole molecules, no part-molecule separating off 

 till in the act of combining with a new partner. It is limited 

 to this, and there is no mention of separate part-molecules, 

 dissociation theories, or so-called free ions. Therefore, though 

 the dissociation theory has been frequently referred to as the 

 Williamson- Clausius hypothesis, it is not supported in any way 

 by Williamson's paper. 



From these considerations it would appear that both the 

 necessity for and the probability of the hypothesis put forward 

 by Clausius are very doubtful. 



Turning now to more modern views, I have already pointed 

 out in the ' Electrician ' for April 19, 1889, that an experi- 

 ment considered by Prof. Ostwald as serving to remove the 

 last doubts as to the validity of the assumption of free elec- 

 trically-charged atoms of chlorine and potassium *, is of a 

 purely negative kind, and throws no new light on the subject 

 at all. 



An experiment is described by the same author in the 

 Zeitschrift fur pht/sikalische Chemie, vi. p. 72, which on 

 examination appears to be of a similar kind. It is given as 

 evidence touching the assumption that a semi-permeable wall, 

 interposed between two electrolytes in the path of a current, 

 will permit certain ions to pass but not others ; and it is 

 further intended to decide as to what will happen under these 

 circumstances. It is assumed that in such a case either no 

 current will pass, or else the ions must give up their charge 

 through the semi-permeable wall, which then acts as a metallic 

 electrode. 



Briefly, the experiment is as follows : — Two vessels con- 

 taining copper-sulphate solution were joined by a siphon full 

 of potassium-ferrocyanide solution, its ends being closed by 

 parchment-paper. A deposit of copper ferrocyanide formed 

 in the pores of the paper. This arrangement was placed in 

 circuit with a battery and galvanometer. A current of 10° 



* ' Outlines of General Chemistry,' p. '27o. 



