[MACGREGOR] DEPRESSION OF THE FREEZING-POINT 17 
case of the electrolytes examined. The following table contains the 
_ values of k and / for the electrolytes considered above, and the depression 
constants obtained from these values, for the undissociated molecules and 
the free ions respectively. In the case of the sulphates, as the solutions 
are fairly dilute, the assumption is made that they dissociate into three 
free ions, although the positive differences in the case of the sulphates in 
Table I would seem to make it probable that the dissociation is in part 
into two free ions. 
TABLE III. 







Ionization Constants. Depression Constants for : 
Electrolyte. TER PAPERS 
k l pag eeecated Free Ions. 
K Cl 2°032 3°682 2°032 1°841 
Na Cl. 2°071 3°741 | 2°071 1871 
H Ci (ist ser.) 1:564 3°664 1°564 1°832 
H Cl (2nd ser.) 1°433 3°700 | 1433 1°850 
Ke SO, 1°097 2°780 2°194 1-853 
Nas SO; 1°098 2°812 2°196 1°875 
HI, SO, 0°881 2°746 1°762 1°831 



As seen above, the values of the depression produced by molecules 
may be expected to be wide of the mark, while those for the free ions 
may be expected to be much closer. One sees at a glance that the 
latter have very nearly the value which they are expected from a 
theoretical stand-point to be found to have when accurately determined. 
It is interesting to note that the values obtained for potassium chloride 
and sodium chloride are in close agreement with Raoult’s' results, 
obtained by an entirely different method which makes no use of ionization 
coefficients. This distinguished experimenter made a series of observa- 
tions of depression on dilute solutions of these electrolytes, and having 
plotted his molecular depressions against the depressions themselves, he 
obtained curves exhibiting rapid curvature in the region of great dilution. 
By producing these curves beyond the range of observation until they 
cut the axis of molecular depression, he found the molecular depression 
for infinite dilution to be about 36°8 for potassium chloride and 37-2 for 
sodium chloride. 
It is usually assumed, by analogy from the results of observations on 
non-electrolytes of different kind and constitution, that the depression 

1 Loc. cit. 
R Sec. III., 1900. 2. 
