III. ON THE DEPRESSION OF THE FREEZING-POINT BY 

 MIXTURES OF ELECTROLYTES. BY JAMES BARNES, B. A., 



Dalhoiisie College, Halifax, N. S. 



(Communicated by Professor J. G. MacGregor on March 12th, 1900.) 



In a 1 paper communicated last winter to this Society, Mr. 

 E. H. Archibald described experiments he had made to test the 

 ionization coefficients, obtained by 2 Prof. MacGregor's method, 

 for mixtures of equimolecular solutions of two electrolytes 

 having an ion in common. With these coefficients and Yan't 

 Hoff's constant as data, he calculated the depression of the 

 freezing-point of the mixtures ; and he then compared the 

 calculated with the experimental values. It was found that the 

 difference between these values was, in general, equal to the 

 arithmetic mean of the differences between the calculated and 

 experimental values of the depressions of the constituent simple 

 solutions, and the test was therefore concluded to be satis- 

 factory. 



At Prof. MacGregor's suggestion, I undertook similar 

 experiments with mixtures, not of equimolecular solutions, 

 but of solutions of different concentrations. The electrolytes 

 selected were potassium chloride, sodium chloride, and hydro- 

 chloric acid. 



In the case of mixtures of solutions which are not equi- 

 molecular Mr. Archibald's method of testing the ionization 

 coefficients is not applicable. I found it necessary, therefore, to 

 obtain an expression for the depression of the freezing-point for 

 such mixtures in terms of the ionization coefficients. 



In a simple solution containing n gramme-molecules of an 

 electrolyte per litre, if a is the ionization coefficient, the 

 number of dissociated molecules is n a and the number of undis- 

 sociated (1 a) n. If a molecule of this electrolyte breaks down 



1 Trans. N. S. Inst. Sci., 10, 33, 

 * Ibid., 9, 101, 1895-96. 



(139) 



