110 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



So far as possible the same electrolyte, namely sodium iodide, has been 

 employed for- the purpose of comparison. In a few cases, however, 

 results with this electrolyte are not available and the data for other 

 iodides are therefore given. If the speed of the ions is solely a function 

 of the viscosity of the solvent and is independent of the nature of the 

 electrolyte, the nature of the solute will have no influence on the ratio of 

 conductance to fluidity. As we shall see below, this is not the case. 2 

 On examining the table it will be seen that the limiting value of the 

 conductance is roughly proportional to the fluidity of the solvent. The 

 ratios A /F given in the last column vary between 0.338 for isoamyl- 

 alcohol and 1.173 for water. These are, however, extreme values, and in 

 the greater number of cases the ratio has a value of approximately 0.6. 

 The three inorganic solvents, water, ammonia and sulphur dioxide, show 

 exceptionally high values of the conductance-fluidity ratio. The 

 higher alcohols have exceptionally low values, the value in general 

 being the smaller the more complex the alcohol. In comparing 

 the A values of the salts in different solvents, we are comparing the 

 sum of the conductances of the two ions. We may therefore expect 

 to obtain a more nearly comparable result if we compare the con- 

 ductances, not of the electrolytes, but of the individual ions of the elec- 

 trolytes. The ratios of the ionic conductances for the different ions in 

 ammonia and in water have been given in Table V. An examination of 

 that table shows that the ratios of the ionic conductances vary all the 

 way from 2.03 to 3.36, while the ratio of the fluidities of the two solvents 

 is 4.15. It follows, therefore, that the ratio of the A values for a given 

 electrolyte in different solvents cannot be a constant, since the ratios of 

 the ion conductances vary for different ions. 



If a comparison is to be made between the conductance and the 

 fluidity of electrolytes in different solvents, it might be expected that 

 more nearly comparable results would be obtained if the more slowly 

 moving ions were chosen for the purpose of comparison. For example, 

 in water at 18, the ratio of the conductance of the acetate ion to the 

 fluidity of water is 0.367, 3 while in ammonia the ratio of the conductance 

 of the CH 3 CONH~ ion to the fluidity of ammonia at its boiling point 

 is 0.330. 



Apparently, therefore, the ratio of the ionic conductance to the 

 fluidity of the solvent approaches a constant limiting value somewhere 



Walden [ZtacTir. f. phya. Chem. 78, 257 (1912)] believes to have shown that, with a 

 few exceptions, the ratio \ /F is constant. In this he has been misled as a result of 

 employing A values obtained by extrapolating with the cube root formula of Kohlrausch 

 which is not applicable. 



a Based on the value 34.6 for the conductance pf the acetate ion. Johnston. J. Am 

 Chem. SQC. 31, 10JO (1909), 



