DEPRESSIONS FOR ELECTROLYTES MACGREGOR. 213 



Owing to ionization, the curve of an electrolyse will differ 

 from that of a non-electrolyte, (1) because of the change thereby 

 produced in the number of molecules (including free ions) in unit 

 of volume, and (2) because of the change produced in the dis- 

 turbing influences referred to. The former change is doubtless 

 the more important, and I shall assume the latter to be negligible 

 for the present purpose. Now dissociation increases continu- 

 ously with dilution. If, therefore, association of molecules does 

 not occur, and if the mode of ionization does not change, the 

 equivalent depression must be increased by the dissociation, in a 

 ratio which increases continuously with dilution. The change 

 produced in the curve by dissociation, therefore, will be a shear 

 parallel to the equivalent depression axis, and increasing with 

 dilution. The resulting curve will consequently remain convex 

 towards the axis of dilution, but it will be less likely than the 

 curve of a non-electrolyte, to exhibit the minimum point. 



If, now, we plot equivalent depression against ionization 

 coefficient, instead of dilution, the result will be the same as if 

 we shortened the dilution ordinates of the various points of the 

 curve just mentioned, in ratios increasing with the dilution, 

 which process must leave the curve convex towards what was 

 the dilution axis, but is now the ionization coefficient axis. 



If, therefore, no change occur in the association of molecules 

 or in the mode of ionization, the curve of an electrolyte on the 

 diagram must start at the intersection of its tangent line, tangen- 

 tially to that line, and bend away from it, as dilution diminishes, 

 to the right, possibly passing through a point of minimum 

 equivalent depression. We may speak of such a curve as the 

 normal curve for the tangent line, corresponding to the given 

 conditions as to constitution in solution, and mode of ionization. 



If, the constitution of the electrolyte in the solution remaining 

 constant, the mode of ionization changes as dilution diminishes, 

 say, in such a way that the molecules dissociate, on the average, 

 into a smaller number of ions, the equivalent depression will 

 diminish more rapidly than it otherwise would. The curvature 

 of the curve will therefore diminish, and may possibly become 



