114 ON THE VISCOSITY 



1 Professor MacGregor has pointed out that, both on theoretical 

 grounds and because of the way in which the ionization coeffi- 

 cients and such physical properties as specific gravity, viscosity, 

 etc., in general, vary with the concentration in simple solutions, 

 it is to be expected that the value of any such property, for a 

 simple solution which is so dilute that the dissociated and undis- 

 sociated molecules may be regarded as without mutual action, 

 will be expressed by the formula : 



P = P W + k(l-a)n + lan ................. (1) 



where P is the numerical value of the property for the solution, 

 Pio that of the same property for water under the same physical 

 conditions, n the concentration expressed in gramme-equivalents 

 per unit volume, a the ionization coefficient of the electrolyte 

 in the solution, and /.' and I constants, called ionization constants. 

 He has further shown that the value of a property for a 

 mixture of two electrolytes will be given in terms of the values 

 of the ionization constants as determined for the simple solu- 

 tions, by the expression : 



+ fk, (\-a,) n, + l, a,n,) ->- "I . . (2) 



V / fj -f- V% J 



where the n's are the concentrations of the constituent solutions 

 (the electrolytes being indicated by 1 and 2), the as the ioniza- 

 tion coefficients of the respective electrolytes in the mixture, the 

 ?/s the volumes of the constituent solutions, and p the ratio of 

 the volume of the mixture to the sum of the volumes of the 

 constituent solutions. 



The application of the first expression to simple solutions is, 

 as 2 Prof. MacGregor has shown, of little theoretical interest; but. 

 that of the second to mixtures, because of its being based on 

 the dissociation theory and involving no arbitrary constants, is 

 of very considerable interest. It is the applicability of this 

 expression (2) that the present paper is intended to test with 

 mixtures of solutions of the above-mentioned salts. 



1 Trans. N. S. Inst. Sci., 9, 219, 1896-97. 



2 Trans. N. S. Inst. Sci., 10, 61 (foot note), 1898-99. 



