VI.—ON THE CALCULATION OF THE CONDUCTIVITY OF AQUEOUS 
SOLUTIONS OF PorassiUM-MAGNESIUM SULPHATE.—By 
T. C. McKay, B. A., Dalhousie College, Halifua, N. S. 
(Read March 9th, 1898.) 
The measurements and calculations, the results of which are 
given in this paper, were made with a view to finding out 
whether the conductivity of solutions of the double sulphate of 
potassium and magnesium could be calculated on the supposition 
that it separates on solution in water into potassium sulphate 
and magnesium sulphate. The research was undertaken at the 
suggestion of Professor MacGregor, and carried out in the physical 
and chemical laboratories of Dalhousie University. 
The method by which the calculation of the conductivities 
was made is based on the dissociation theory of electrolysis, and 
was devised by Professor MacGregor for the calculation of con- 
ductivities of mixtures of two electrolytes containing a common 
ion.* The writer showed in a former papert that by the use of 
this method of calculation, the conductivity of mixtures of solu- 
tions in water of the chlorides of sodium and barium could be 
calculated on the supposition that the two salts exist separately 
in the solution. Most of the experimental methods used in the 
present research were described in that paper, and need not be 
referred to here. 
The potassium sulphate used in the determinations was 
obtained from Eimer & Amend, New York; the magnesium 
sulphate, partly from Eimer & Amend and partly from Merck. 
All the salt obtained from the former was recrystallized once. 
Merck’s magnesium sulphate was his guaranteed reagent, and 
with the exception of that used for some MgSO, solutions from 
5 to 1 gramme-equivalent per litre, was not recrystallized by 
the writer. The salts were tested with silver nitrate for the 
2, 
*Trans. N.S. Inst.Se., Vol. [X., p. 101. 
y Imstises, wWiol. LX.; prozle 
+Trans. N.S. 
(348) 
IZ, 
