Chapter XII. 

 Theories Eelating to Electrolytic Solutions. 



1. Outline of the Problem Presented by Solutions of Electrolytes. 

 The problem of electrolytic conduction presents a twofold aspect depend- 

 ing upon the point of view from which it is approached. On the one 

 hand, we are concerned with certain well defined equilibria, the laws 

 governing which it is attempted to discover; on the other, we are con- 

 cerned with the mechanism of the process whereby the conduction of the 

 electric current is effected. In the first case the principles governing 

 equilibria in mixtures are applied, supported by various auxiliary assump- 

 tions which are necessary if an explicit solution of the problem is to be 

 reached. These assumptions usually involve the equation of state of 

 the system, the precise form of which is not known. A general solution, 

 therefore, cannot be reached by this method. In order to disclose the 

 mechanism of the conduction process, a knowledge of the forces acting 

 between the conducting particles and their surroundings is required. 

 Since the laws governing these forces are not known, a solution is not 

 possible by this method. Furthermore, if a force function is assumed, 

 a solution can be reached only by the application of statistical methods 

 and these methods have not been developed to a point where their appli- 

 cation to electrolytic systems can be made with any degree of certainty. 

 In either case, therefore, a point is soon reached where the results ob- 

 tained are little more than conjectures. The probable correctness of the 

 results obtained may be checked by comparison with experiment. In 

 practice it is often found that, while the results of one method agree 

 fairly well among themselves, they disagree with those obtained by the 

 alternative method. That the two methods must lead to results which 

 are in mutual agreement is not to be doubted. Lack of agreement indi- 

 cates that various assumptions made are not permissible. 



It may be expected that a solution of the problem will first be reached 

 for mixtures where the concentration of the electrolytic component is so 

 % low that various effects, due to the interaction of the ions and other mo- 

 lecular species present, become negligible. Here, however, the difficulty 

 arises that experimental data become very uncertain. Nevertheless, ap- 



323 



