VII. ON A DIAGRAM OF FREEZING-POINT DEPRESSIONS FOR 

 ELECTROLYTES. BY PROF. J. G. MACGREGOR, Dalhousie 

 College, Halifax, N. S. 



(Received June 20th, WOO.) 



The object of this paper is to describe a diagrammatic method 

 of taking a bird's-eye view of such knowledge as we possess of 

 the relation of the depression of the freezing-point to the state 

 of ionization in aqueous solutions of electrolytes, and to show 

 that such diagrammatic study gives promise of throwing much 

 light upon the following questions: (1.)* Has the depression 

 constant a common value for all electrolytes, and if so, what 

 is it ? And (2), What is the state of association, and what the 

 mode of ionization of electrolytes, in solution ? 



Construction and Properties of the Diagram. . 



If an extremely dilute solution contain an electrolyte whose 

 molecule, as it exists in solution, contains p equivalents, and dis- 

 sociates into q free ions, and if a is its ionization coefficient and 

 k its depression constant, the equivalent depression will be : 



If therefore we plot a diagram of curves with ionization coeffici- 

 ents as ordinates, and equivalent depressions as abscissae, the 

 resulting curves must, at extreme dilution (a = 1), be tangential 

 to the straight lines represented by the above equation, provided 

 the proper values of k, p, and q be employed. These straight 

 lines, which, for shortness, we may call the tangent lines of the 

 curves, can readily be drawn in the diagram, with any assumed 

 value of k, and on any admissible assumptions as to the values 

 of p and q. In the diagram on page 235 the dashed lines are the 



* On this question, see also a paper recently communicated to the Royal Society 

 of Canada, and to be published in its Transactions for 1900. 



(211) 



