OF DILUTE SOLUTIONS OF ELECTROLYTES. HEBB. 429 



when the over-cooling is zero. For this purpose I took a solu- 

 tion and found its depressions for different over-coolings. These 

 depressions I plotted as ordinates against the over-coolings as 

 abscissae. This gives practically a straight line which, if pro- 

 duced to cut the depression axis, cuts off a portion from it 

 representing the depression when the over-cooling is zero, 

 Raoult has shewn that the following relation holds for solutions 

 of different concentrations 



C 1 =C(1+KS) 



where C 1 is the observed depression for over-cooling S, C is the 

 depression for over-cooling zero, and K is a constant. Hence. 

 determining C and S for different solutions, and knowing K to 

 hold for all solutions, we can find C in each case. I determined 

 K to have the value .02. Hence it can easily be seen that for an 

 over-cooling of .1 degree the values of the depressions will be 

 .02% too great. 



The ionization coefficients are taken from a paper by 

 Whetham.* Since he only carried his concentrations to .03 

 gramme-equivalents per 1000 grammes of solution, I have 

 extended the curve under guidance of extrapolated values given, 

 by Dr. MacGregor.-f* He obtained his extrapolated values by 

 plotting, alongside of one another, the ionization coefficient- 

 concentration curves for and 18 the latter being obtained 

 from data given by Kohlrausch. 



In the following table the concentrations are given in 

 gramme-equivalents per litre of solution at OC. The depressions* 

 which have been corrected for over-cooling, as pointed out, are 

 given in degrees Centigrade. The ionization coefficients are for 

 0C., and the equivalent depressions are the depressions in 

 degrees Centigrade divided by the concentration in gramme- 

 equivalents per litre of solution at 0C. The letters i and e after 

 the coefficients shew whether they were obtained by interpola- 

 tion or extrapolation. 



* Loc. cit. 



t Proc. and Trans. N. S. Inst. Sci., Vol. X. p. 218. 1899-90. 



