88 Theory of Electrolytic Conduction of Clausius. 



and a salt solution, we may have in each pore a small voltaic 

 circuit composed of the cupric ferrocyanicle as metallic con- 

 ductor, and the two liquids as electrolytes. That very unusual 

 phenomena may arise in a minute circuit of this kind is already 

 shown by the copper-zinc couple of Gladstone and Tribe. But 

 whatever the actual process may be in this osmotic-pressure 

 experiment, it is evident there is more to be considered than 

 the mere smallness of the pores. 



In the B. A. Eeport, 1890, p. 333, Prof. Ostwaid concludes 

 that one consequence of the dissociation hypothesis is that 

 "in general water must show against every electrolytic 

 solution the potential of the faster ion;'"' and that this is 

 confirmed by the experiments of Xernst and of Planck at 

 references given. In Planck's paper he does not appear to 

 have made any experiments himself, and those of other authors 

 referred to were carried out by means of metallic poles 

 immersed in the liquids, and so introducing the unknown 

 quantity of metal-liquid contacts. The experiments of Nernst 

 appear to have the same defect, and, in addition, to refer only 

 to circuits containing three or more liquid contacts, and can- 

 not give any definite information about individual contacts. 



This evidence is therefore also of a purely indecisive 

 character. 



In the same Eeport, p. 335, the same author states that 

 " according to Faraday's law all chemically equivalent amounts 

 of positive and negative ions are charged with equal amounts 

 of electricity." One could wish that Prof. Ostwaid had given 

 a reference to Faraday's statement of this " law." 



In the Philosophical Magazine for August 1891, Prof. 

 Ostwaid describes some cases of what he terms chemical 

 action at a distance in the following form of experiment. He 

 points out that while pure zinc is scarcely acted on by a 

 solution of common salt alone, yet in a circuit consisting of 

 zinc, salt solution, hydrochloric-acid solution, platinum, 

 the zinc dissolves when connected to the platinum, i. e. 

 by the action at a distance of the acid. There is certainly, 

 as Prof. Ostwaid partly admits, nothing new in this form of 

 experiment. It is as old and familiar at least as the Grove's 

 battery, and the action is commonly explained on the old 

 theory of consecutive molecular interchanges coupled with 

 considerations of the thermo-chemical relations of the acting 

 bodies. Prof. Ostwaid brings it out as speaking forcibly for 

 the value of the " free ion " theory, assuming that the action 

 depends primarily on the passing into the solution of posi- 

 tively charged atoms from the zinc, but states that it cannot 

 be explained how the charging takes place, or in what it 



