VI. ON THE CALCULATION OF THE CONDUCTIVITY OF AQUEOUS 



SOLUTIONS OF POTASSIUM-MAGNESIUM SULPHATE. BY 

 T. C. McKAY, B. A., Dalhousie College, Halifax, 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 paper f 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 MgS0 4 solutions from 

 .5 to 1 gramme-equivalent per litre, was not recrystallized by 

 the writer. The salts were tested with silver nitrate for the 



*Trans. N. S. Inst. Sc., Vol. IX., p. 101. 

 tTrans. N. S. Inst Sc., Vol. IX., p. 321. 



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