Electrolytic Conduction of Olausius. 83 



practically that, according to it, electrolytes could not obey 

 Ohm's law for a gradually increasing electromotive force; 

 whereas according to Clausius they do obey Ohm's law if, 

 as is carefully pointed out in a footnote, we consider only 

 the force acting in the interior of the electrolyte, and not 

 that at the electrodes, where the products of decomposition 

 are separated and polarization has to be overcome. 



But we may ask, Is this an admissible limitation ? Is it 

 allowable, when considering a process of decomposition, to 

 expressly leave out of account the only parts of the mechanism 

 where decomposition visibly occurs, viz. the electrodes? If 

 the whole system be taken into consideration, electrolytes do 

 not of course obey Ohm's law, and a more or less abrupt rise 

 in the ratio of current to E.M.F. does take place when a 

 gradually increasing E.M.F. reaches a point which, speaking 

 generally, has a relation to the heat of combination of the 

 decomposing body*. 



Below this point the current which accompanies smaller 

 E.M.F.'s is, no doubt, accompanied by decomposition ; but 

 of what ? Can it be shown, for instance, that when a minute 

 E.M.F. produces a continuous current through HC1 solution, 

 it decomposes HC1 or any other substance of considerable 

 heat of formation; and that the current is not more probably 

 conducted by decomposition of impurities, hydrates or com- 

 plex molecules, whose parts have minute attractions for each 

 other ; or that, supposing HC1 is decomposed, the action is 

 not masked by the well-known secondary effect of dissolved 

 oxygen or other " depolarizer/' 



On considering the whole electrolytic system, then, this 

 second objection must also be put aside, and in so far Olausius 

 cannot be said to have shown the need of a new hypothesis |. 



The probability of the new hypothesis proposed by Olausius, 

 as described in §§ 7 and 8, may, however, be considered. In 

 §7 we are asked, without any previous explanation, to con- 

 sider a positive part-molecule, and to assume that its electric 

 state remains the same after separation from the complete 

 molecule. This is the first reference in the paper to such a 

 single separate electrified part-molecule. It is described as 

 moving about among the other complete molecules ; but no 

 explanation appears to be given before as to how such a thing 

 came to exist. It is explained, however, in detail that these 



* This was illustrated by a set of curves for the decomposition of 

 various electrolytes given by the present author, Phil. Mag-. June L891. 



f In pointing out the invalidity of these objections, it is not intended 

 to acquiesce in the pure Grotthus theoiy. The modification of it pit 

 forward bv Faraday is probablv much nearer the truth. 



a 2 



