LAWS OF ELECTROLYTIC DISSOCIATION 7 



The question may be raised: within what limits of concentra- 

 tions may the mass law be used without corrections? In solutions 

 of non-electrolytes of 0.1 molar concentration the error is insig- 

 nificant, while it is within allowable limits even in solutions of 

 molar concentration. It has been recently found that these errors 

 or deviations become much greater as soon as one deals with ionized 

 solutions. Since relatively large deviations have been discovered 

 between the ionic equilibrium and the mass law, this fact has to 

 be taken into consideration. 



As unportant as these corrections are whenever the determina- 

 tion of exact numerical figures is involved, nevertheless the fact 

 cannot be over-emphasized that in most cases they are very small. 

 It is, therefore, essentially justifiable to develop first the compli- 

 cated system of ionic equilibrium on the basis of the simple law of 

 mass action, and then subsequently to explain when and how the 

 necessary corrections are to be applied. 



2. Electrolj^ic dissociation 



The publication in 1887 by Svante Arrhenius^ of the theory of the 

 dissociation of the electrolytes marked the beginning of a new era 

 in physical chemistry. A great mass of facts which had been 

 awaiting a proper explanation became at once comprehensible. 

 The astounding range of importance of this theory is best illustrated 

 by the fact that the number of its consequences is still growing even 

 at present, and all of this part of the book represents but one series 

 of such consequences. The context of the Arrhenius hypothesis is 

 briefly this: The conductivity of an electrolyte in solution does not 

 depend, as it had been hitherto assumed, on its decomposition by 

 the current into ions, but upon the spontaneous splitting of at 

 least part of the electrolyte into ions, when it is brought into solu- 

 tion. These ions may be regarded as independent molecules; their 

 interreactions obey the usual law of mass action, which was first 

 elaborated by Guldberg and Waage and then chiefly by van't 

 Hoff. 



Until recently the origin of the opposite free electric charges 

 in dissociated solutions was not clear. The following explanation 

 had been offered-: Space was imagined to be filled with electrically 



^ Svante Arrhenius, Zeitschr. f. physikal. Chem. 1, 631 (1887). 

 * W. Nernst, Theoretische Chemie (the older German editions). 



