118 ON THE CALCULATION OF THE CONDUCTIVITY OF 



belong only. They must rather be. regarded however as passing 

 in rapid alternation, now through a region occupied by one 

 solution, and now through a region occupied by the other. The 

 actual mean velocities of the ions in the mixture will therefore 

 probably differ from their values in a solution of their own 

 electrolyte only. In the case of dilute solutions the difference 

 will be small, in sufficiently dilute solutions inappreciable, but in 

 the case of the stronger solutions it may account in large part 

 for the discrepancy observed above. We have however, so far 

 as I am aware, no data for calculating the effect of mixture on 

 the ionic velocities or the extent to which the discrepancy is due 

 to this effect. 



To obtain some rough conception of its magnitude, I have 

 calculated the conductivity of the mixture No. 18, on two 

 assumptions which seemed more or less probable, viz., (1) that 

 the velocities of the ions of each electrolyte in the mixture are 

 the same as they would be in a simple solution of their own 

 electrolyte of a concentration (in gramme-molecules per litre) 

 equal to the mean concentration of the mixture, and (2) that the 

 velocities of the ions of each electrolyte, when passing through a 

 region occupied by the other electrolyte, are the same as they 

 would be in a simple solution of the former of a dilution equal 

 to that of the latter. The expression used for the conductivity 

 wa 



p 



2 p 



where u l and u 2 are the sums of the velocities of the ions of 

 electrolytes 1 and 2 respectively in simple solutions of the 

 dilutions which they have in the mixture, while u^ and u 2 ' are 

 the values these ionic velocities would have according to the 

 particular assumption employed, the velocities in all cases being 

 those corresponding to the same potential gradient. As the 

 graphical process above gave the dilution of each electrolyte in 

 the mixture, the values of u and u were readily determined by 

 the aid of Kohlrausch's table of ionic velocities.* I found that 



*Wiedemann's Annalen, L, p. 385, (1893). 



