320 CONDUCTIVITY OF AQUEOUS SOLUTIONS.—ARCHIBALD. 
dilute mixtures. But the fact that the differences are so large 
where a double salt may exist, would seem to furnish evidence 
for the assumption, that in the more concentrated solutions of 
the double Sulphate of Potassium and Copper, the molecules of 
the double salt are not all broken up, but exist to some extent 
as a double salt in the solution. 
For solutions of the Copper-Potassium sulphate, more dilute 
than 0.1 equivalent gramme-molecules per litre, as for the Zine- 
Copper and Sodium-Potassinm sulphate mixtures, through as 
wide a range of dilution as here examined, the differences are 
within the limit of observational error and change sign fre- 
quently, which seems to show that they are due to accidental 
errors. It is thus possible to caleulate the conductivity of these 
solutions and mixtures; and it would follow that, as far as the 
conductivity measurements can show, for the more dilute solu- 
tions of Copper-Potassium sulphate there is no double salt 
existing as such in the solutions. 
