﻿308 Profs. J. N. Mukherjee and 13. 0. Papaconstantinou on 



Since only " e " is variable, a comparison of the coagu- 

 lation time " t " for the same change in the sol makes it 

 possible to determine the variation in the percentage of 

 successful collisions and its dependence on the conditions 

 of experiment. When the maximum rate is reached, e = l 

 and hence a measure of the absolute value of e is possible. 



Problems awaiting solution. — A. glance through the experi- 

 mental work would show that the assumption of the constancy 

 of "T" is not well justified. The simplicity of Smolu- 

 cbowski's equations consist in that there is only one constant. 

 The experimental limitations are great, and it is quite possible 

 tbat the discrepancies are due to the defects of the ultra- 

 microscopic method. The other possibility is that the 

 simplifying assumptions of Smoluchowski — for example, 

 the constancy of "T" independent of the stage of co^ 

 alescence — are not true within narrow limits. Tt is of 

 great interest to know the limits within which these 

 equations are valid. 



The important questions that await solution in this 

 connexion are : 



{a) the limits within which the above equations are 

 valid ; and 



(b) if the above equations are valid, the variation of e 



with concentration of electrolyte ; 



(c) the dependence of e on the electric charge ; 



(d) the variation of e with temperature. 



In the following an account of an attempt to examine 

 these factors, with the exception of (c) , is recorded. 



Indirect Methods. — Variations in physical properties that 

 occur simultaneously with the process of coagulation can be 

 utilized to measure the rate of coalescence. 



Smoluchowski pointed out that the viscosity measure- 

 ments of Gann (Koll. Chem. Beihefte, vol.viii. p. 67 (1916)) 

 do not satisfy the main requirements of his equations — 

 namely, a similarity in the form of the curves (showing the 

 variation in viscosity with time) independent of the nature 

 of the electrolyte. He concludes that viscosity changes do 

 not form a measure of the coagulation process. Yet he 

 considers that the method is suitable for a quantitative 

 comparison of the effect of various concentrations on the 

 values of e when the curves are similar. 



The variation in physical properties, however, is likely 





