FORM OF THE CONDUCTANCE FUNCTION 89 



that all liquid substances are capable of ionizing substances dissolved in 

 them quite irrespective of what their properties may be. The only con- 

 dition necessary in order that the solution shall conduct the current is 

 that the electrolyte shall be sufficiently soluble so that a highly concen- 

 trated solution may be obtained. We have seen, in the preceding section, 

 that in solvents which have a low ionizing power the conductance de- 

 creases with decreasing concentration, and appears to approach a value 

 of zero. If the electrolyte, therefore, is not very soluble, its influence on 

 the conductance of the solvent will be inappreciable. If, however, an 

 electrolyte is soluble up to concentrations as high as normal, then its 

 solutions will in all cases be found to conduct the current. In general, 

 the typical inorganic electrolytes are not soluble in weak ionizing agents, 

 but certain organic electrolytes, such as the salts of organic bases, are 

 quite soluble and yield solutions which conduct the current. It is prob- 

 able that all liquid dielectric media to some extent possess the power of 

 ionizing substances dissolved in them. 



The difference between the properties of solutions of electrolytes in 

 different solvents does not consist in a power to ionize an electrolyte in 

 one case and the entire absence of this power in another, but rather in 

 a difference in the form of the conductance curve which varies with the 

 nature of the solvent, either with its constitution or with its temperature. 

 That property of the solvent which appears to control the form of the 

 conductance curve is the dielectric constant. Thomson 15 and Nernst 16 

 first suggested that the ionizing power of a solvent is determined by its 

 dielectric constant. This constant, however, is by no means to be taken 

 as a measure of the ionizing power of a solvent, for the ionization curve 

 of a given electrolyte is a complex function of the concentration and the 

 relative ionizations will vary with the concentration. At very high con- 

 centrations the relative ionizations will, in general, differ much less than 

 at low concentrations. Indeed, in the preceding section we saw that the 

 constant D determines the ionization at very high concentrations and 

 that, therefore, for a given electrolyte in different solvents there is a 

 certain concentration at which the ionization of this electrolyte will be 

 practically the same in all solvents. What we must expect to find, there- 

 fore, is that the form of the conductance curve is determined by the 

 dielectric constant of the solvent. The relation between the conductance 

 and the dielectric constant is therefore shown most readily by bringing 

 out the relation between the constants of the conductance function and 

 the dielectric constant. In the following table are given values of the 



"Thomson. Phil. Mag. [5] 36, 320 (1893). 

 "Nernst, Ztschr. f. phys. Chem. IS, 531 (1894). 



