70 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



in solution in the two solvents. Since only two observations were made, one 

 at and the other at 25, the variation in conductivity is shown by a straight 

 line. If observations at intermediate points could be obtained, the line would 

 probably be curved. The first ordinate that at is made the same in 

 both cases. The second in the case of the conductivities is then found from 

 the observed value by multiplication by a factor. 



From an inspection of fig. 15 it is evident that the lines representing va- 

 riation of conductivity and variation of fluidity with temperature are almost 

 coincident. That is, the temperature coefficients are almost the same in 

 both, the difference never being over 8 per cent, and in most cases much 

 less than this, particularly for solutions in ethyl alcohol. Vollmer has 

 already called attention to this fact. This amounts, then, to a proof of the 

 Kohlrausch hypothesis for solutions in methyl and ethyl alcohols, and such 

 proof is necessary to establish the validity of the one proposed. 



It has already been shown that this is also true for certain electrolytes in 

 certain mixtures of solvents. Though the temperature coefficients of fluidity 



and conductivity are the same, the value of the quotient is much greater 



Of 



for an electrolyte in the mixture than for the same electrolyte in the pure 

 alcohol. It is difficult to see why this is the case, unless it be that in the 

 mixture we have a complex solvent not to be compared with the simple one. 

 Certainly the presence of compounds in the mixture would complicate mat- 

 ters. This interesting point needs further investigation. 



Knowing the values of the constant for the pure solvent, and assuming the 

 validity of the relation for the mixture, we might calculate the ionic friction. 

 This would not be the same as the coefficient of viscosity of the mixture, 

 but its variation with temperature would be identical with that of con- 

 ductivity. 



The next step is the discussion of certain data as to conductivities in the 



two solvents proof that the expression holds for solutions in these 



solvents. The values for the coefficients of viscosity have for the most part 

 been taken directly, or interpolated from the results of Thorpe and Rodger. 1 



The values for the conductivities in the various solvents are taken from 

 observations of Vollmer, 2 Carrara, 2 Jones and Lindsay, 2 and others, and from 

 our own. 



The values for the association factors are those given by Ramsay and 

 Shields in their first paper, 3 at ordinary temperatures for methyl alcohol 

 3.43, for ethyl alcohol 2.74. 



1 Phil. Trans., 185 A, 397 (1894). 2 Loc. cit. 



3 Ztschr. phys. Chem., 12, 433 (1893). 



