92 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



of the constant K if sufficiently accurate data are available at inter- 

 mediate concentrations. The value of K for solutions in ethylamine was 

 obtained in this way. The extremely low value of the constant will be 

 noted. 



Having shown the relation between the constants of the conductance 

 function and the dielectric constant, it will be unnecessary to give a 

 detailed list of various solvents which have been found to yield electro- 

 lytic solutions. The general form of the conductance curve may at once 

 be inferred from the value of the dielectric constant. Many salts are 

 not, as a rule, soluble in solvents of low dielectric constant. Neverthe- 

 less, certain typical salts form solutions with many solvents of very low 

 dielectric constant, as for example silver nitrate, which dissolves in amyl 

 amine, which has a dielectric constant of only 4.5. Such behavior, how- 

 ever, is exceptional and is probably to be ascribed to the formation of 

 soluble complexes between the salt and the solvent. Various salts of 

 organic bases, however, as has already been stated, are soluble in sol- 

 vents of very low dielectric constant. 



The question has been raised as to the influence of the electrolyte on 

 the dielectric constant of the medium in which it is dissolved. Walden, 17 

 who has measured the dielectric constants of some non-aqueous solutions, 

 concluded that the dielectric constant is greatly increased due to the 

 addition of an electrolyte and has suggested that the observed deviations 

 of strong electrolytes from the simple mass-action law are due to this 

 factor. More recently, however, Lattey 18 has subjected the methods 

 of measuring the dielectric constant of electrolytes to careful examina- 

 tion and has himself carried out measurements on numerous aqueous 

 solutions. He finds that the dielectric constant of electrolytic solutions 

 is considerably lower than that of the pure solvent. For example, for a 

 solution of potassium chloride in water of concentration 0.00755 normal 

 he obtained the value 66.25 as against 81.45 for pure water. The dielec- 

 tric constant diminishes approximately as a linear function of the con- 

 centration and the effect for different electrolytes is of the same order 

 of magnitude. Further investigations in this direction are much needed. 



The precise form of the functional relation between the dielectric 

 constant of the solvent and the ionization of the dissolved electrolyte is 

 unknown. Walden 19 has suggested an empirical relation according to 

 which the ionization of a typical electrolyte is the same in different 

 solvents when the product of the dielectric constant and the cube root 



"Walden, Bull. Acad. St. Pctersb. 6, 305 and 1055 (1912) ; J. Am. Chem. Soc. 35, 

 1649 (1913). 



"Lattey, Phil. Mag. 1,1, 829 (1921). 



"Walden, Ztschr. f. phys. Chem. 5k, 228 /1905). 



