OF AQUEOUS SOLUTIONS.—BARNES. 123 
As both Reyher and Wagner regard their results as affected 
by a possible error of about + 3 in the third decimal place, it is 
seen that the agreement between the calculated and observed 
values for all the salts except copper sulphate is very satis- 
factory, the differences being well within the limit of experi- 
mental error. In the case of copper sulphate, the agreement 
is not so satisfactory. But it was noticed on plotting the 
observed values against the concentration that the points do not 
lie on a smooth curve, and that the point corresponding to the 
concentration 0.5 is at quite a distance from this curve, which 
leads one to think that this observed value cannot be correct. 
The poor agreement in this case might also be partly due to the 
doubtful value of the specific molecular conductivity at infinite 
dilution used. Thus it seems that for all the salts examined, 
copper sulphate perhaps excepted, expression (1) gives the vis- 
cosity of a solution within the limit of experimental error 
throughout a concentration range of 1.0 to 0.125. 
Miatures of Solutions. 
As there is no change of volume on mixing the constituent 
solutions of the above electrolytes of the concentrations given 
below}, and as the solutions mixed were of equal volume and 
also equimolecular, the expression (2) for the value of a property 
in the case of a mixture of two electrolytes with a common ion, 
reduces to: 
P = Py + [hy (1 = Oe) Si l, Diack: I, (=) + 1, a5) . (3) 
where 7 is the concentration of the solutions and the k’s and U’s 
have the values obtained above for simple solutions of the 
respective electrolytes. For the application of this equation to 
the calculation of the viscosity of a mixture, all the quantities 
required are known except the a’s, the ionization coefficients in 
the mixture. 
1See Trans. N.S. Inst. Sci., 9, 125, 1895-96 ; also 9, 297 and 310, 1897-98. 
