320 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



in the critical regions, solvents which have a dielectric constant greater 

 than 26 at ordinary temperatures have fairly high dielectric con- 

 stants in the critical region; and, probably, the higher the dielectric 

 constant of solvents of this* type, the greater the dielectric constant in 

 the critical region. In all likelihood, the dielectric constant of water in 

 the critical region is fairly high. Unfortunately, there are very few data 

 available on the relation between the dielectric constant and the variables 

 which determine the condition of the solvent. 



Among solvents of high dielectric constant, only solutions in water 

 have been measured with any considerable degree of precision. The 

 conductance of solutions in hydrocyanic acid indicates that the behavior 

 of solutions of electrolytes in this solvent is similar to that in aqueous 

 solutions, but available data are not sufficiently accurate to make it 

 possible to determine the precise form of the conductance curve. Fur- 

 ther data on the properties of solutions in solvents of high dielectric con- 

 stant are much needed. 



b. The Relation between the lonization Process and the Constitution 

 of the Electrolyte. While the ionization of an electrolyte is, in the first 

 place, largely dependent on the dielectric constant of the solvent medium, 

 the strongest typical electrolytes are probably ionized in all solvents, 

 provided they are sufficiently soluble, but in solvents of very low dielec- 

 tric constant ionization is appreciable only at high concentrations. The 

 typical inorganic salts are not, as a rule, sufficiently soluble in solvents 

 of low dielectric constant to yield solutions which conduct the current 

 readily. However, salts of various organic bases, such as the substituted 

 ammonium salts 5 * are soluble in solvents of low dielectric constant and 

 conduct the current. 



The dielectric constant is only one of the factors governing the ion- 

 ization process. For ionization is largely dependent upon the nature of 

 the second component. For certain substances, which we ordinarily class 

 as the typical salts, the dielectric constant of the solvent medium is 

 largely determinative of the ionization, but even here we find that in 

 non-aqueous solvents the ionization may vary greatly for salts whose 

 ionization values are practically identical in water. This is true of solu- 

 tions in ammonia and still more so of solutions in acetone. In these 

 solvents, the characteristic properties of the electrolyte persist even down 

 to the lowest concentrations for which measurements exist and these con- 

 centrations are much lower than those in aqueous solutions. No theory 

 of electrolytic solutions can be looked upon as adequate which does not 

 render an account of this very common property of these solutions. 



"Walden, Bull. Acad. Imp. dee Sci,, p. U07, No. 16 (1913), VI series. 



