MIXED SOLVENTS. 15 



non-electrolytes and different electrolytes, but varies also with concentration, 

 and is greatest when dissociation is least. 



Arrhenius concludes that the amount of dissociation is not appreciably 

 changed by addition of small quantities of non-electrolytes. This follows 

 from the fact that the alteration in conductivity is independent of the con- 

 centration. Further, he found that the velocity of inversion of cane-sugar 

 is not appreciably influenced by addition of small amounts of non-electrolytes. 



Holland l worked in the same field as did Arrhenius. His results will be 

 referred to again. Strindberg 2 repeated and confirmed some of Arrhenius's 

 work. 



Wakeman 3 measured the conductivities of various electrolytes, sodium 

 and potassium chlorides, hydrochloric acid, and numerous organic acids, in 

 mixtures of ethyl alcohol and water (containing 10, 20, 30, 40, and 50 per 

 cent of alcohol). 



For the cases studied, the equation 



A 



= constant 



p(100 - p) 



was found to hold, where A is the difference between the conductivity of the 

 electrolyte in water and in the mixture, respectively, and p is the per cent of 

 alcohol by volume. 



Schall 4 determined the conductivity of picric acid in aqueous alcohol. 



Zelinsky and Krapiwin 5 studied the conductivities of sodium and am- 

 monium iodides and bromides in water, methyl alcohol, and a mixture of the 

 two containing 50 per cent of water by weight; for dilutions from v = 16 to 

 v = 1024. Here a striking phenomenon was observed. The conductivities 

 in the 50 per cent mixture were found to be decidedly less than the corre- 

 sponding conductivities in the pure solvents. This minimum is best seen when 

 the results are plotted as curves, with the conductivities as ordinates and the 

 composition of the mixture as abscissae. 



Cohen 6 observed the minimum in the case of potassium iodide. He made 

 a study of the conductivity of potassium iodide in mixtures of ethyl alcohol 

 and water (containing 20, 40, 60, 80, and 99 per cent alcohol). The dilutions 

 ranged from v = 64 to v = 2048. The minimum manifested itself in the 80 

 per cent mixture beyond the concentration v = 512. 



From his own observations, and from those of Wakeman (loc. cit.), he con- 

 cludes that the relation 



w"n 2 ?i = Constant 

 fj. v H 2 O . Ale. 



1 Wied. Ann., 50, 261 (1893). 4 Ibid., 14, 701 (1894). 



2 Ztschr. phys. Chem., 14, 161 (1894). * Ibid., 21, 35 (1896). 



3 Ibid., 11, 49 (1893). Ibid., 25, 31 (1898). 



