70 ROYAL SOCIETY OF CANADA 



The volumes of the simple solutions to be mixed having thus been 

 determined, the mixture may be prepared and its conductivity experi- 

 mentally determined. 



Its conductivity may be calculated by the aid of the expression of 

 the dissociation theory, for the conductivit}' of a complex solution, viz. : 



k = 



jO(t;^4-t;^-|-t,3-i-l,j (^i^i/^X 1 + ^2^2/<X2+ ^h^^Oj^ + ^^4^V'X4) 



where ^ is the ratio of the volume of the mixture to the sum of the 

 volumes of the constituent solutions, which has the value unity if there is 

 no appreciable change of volume on mixing. The value of p may be 

 deterinined b}^ density measurements ; the «'s, iV's and r's are known, as 

 seen above ; and the values of /.ir^ , the specific molecular conductivity at 

 infinite dilution, may in the case of mixtures of sufficient dilution, be taken 

 to be the same as in simple solutions of the respective electrolytes. 



At Prof. MacGrregor's suggestion [ have made a series of observations 

 to test the possibility of calculating the conductivity of solutions contain- 

 ing sodium chloride and potassium sulphate, and, therefore, also sodium 

 sulphate and potassium chloride. These electrolytes were selected because 

 Kohlrausch had determined their specific molecular conductivit}^ at infinite 

 dilution. The observations were conducted in the Physical and Chemical 

 Laboratories of Dalhousie College. 



The work included the purification of the salts and of water, pre- 

 paration and analysis of a series of simple solutions and determination of 

 their conductivity, plotting curves giving the relation of concentration 

 of ions to dilution for these simple solutions, and obtaining from them the 

 dilutions of simple solutions which would have a common concentration 

 of ions, determining the volumes of these solutions to be mixed, prepar- 

 ation of the mixtures, and measuring and calculating their conductivity. 



Purifying the Salts. 



The salts were obtained as chemically pure from Eimer and Amend 

 of New York. After being twice re-crystallized no impurities to any 

 extent could be detected. 



Purification of the Water. 



The water used was ])urifiod by the method described by Hulett,' 

 except that a block-tin condenser w^as used instead of a platinum one. 

 Water purified by this method had at a temperature of 18° C. a conduc- 

 tivity varying from 085 X lO-^" to 0-08 X 10"^^', expressed in terms of the 

 conductivity of mercury at 0° C. 



1 .Tourn. Phys. Chem., Vol. 1, p. 91. 



