114 ON THE VISCOSITY 
1Professor MacGregor has pointed out that, both on theoretical 
grounds and because of the way in which the ionization coeffi- 
cients and such physica! 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=Py+k(l1—a)n+lan,...... ee 
where P is the numerical value of the property for the solution, 
Pw that of the same property tor water under the same physical 
conditions, 7 the concentration expressed in gramme-equivalents 
per unit volume, @ the ionization coefticient of the electrolyte 
in the solution, and /: and / 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 : 
P=Po +5 [(k,l—a)m +h a2) 
1 
UV, + VU, 
: v 
+ (Te, l—a,)n,+l,a,n \ 2 |. 2 
2 ( 2 2 2 2 2 V1 ae Vo ( ) 
where the 7’s are the concentrations of the constituent solutions 
(the electrolytes being indicated by 1 and 2), the a’s the ioniza- 
tion coefficients of the respective electrolytes in the mixture, the 
v'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 frst expression to simple solutions is, 
as ? 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, 1s 
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. 
2Trans. N.S. Inst. Sci., 10, 61 (foot note), 1898-99. 
