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 cf 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 ina 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 
Ue’ 
1 ‘Obee 
p= ay Ny Hon y 1 Sy a, No Ung ; 
2 p U4 We 
where w, and w, 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 w,’ and wu,’ 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 wu and w’ were readily determined by 
the aid of Kohlrausch’s table of ionic velocities.* I found that 
*Wiedemann’s Annalen, L, p. 385, (1893). 
