CONSTANT FOR ELECTROLYTES—HEBB. 421 
others If an estimate could be made of the relative value of the 
various determinations, the weighted mean would give a closer 
approximation to the true values of the depression constants, 
than can be given by a mere average. I have not attempted, 
however, to attach weights to the determinations, being unable 
to do so with any confidence. 
Assuming that averaging will eliminate the greater part of 
the errors we get as the values of m and 7, 1.932 and 1.851 
respectively. The value for 7 is undoubtedly the more accurate 
of the two; and, as we assume that undissociated molecules have 
the same effect as free ions, the value of ™ is to be taken as 
1.851 also, That the average value of m is so much greater 
than that of 2 may be due not only to the defects of the method 
employed in determining it, but to the fact that the bend of the 
curve of an electrolyte is more likely to be to the right than to 
the left, as concentration increases. For it is only where associa- 
tion of molecules takes place that it bends to the left. 
Some of the sets of observations given in the paper, from 
which I have taken my data, I did not use. A few of these 
sets were so erratic that I could make nothing out of them. 
The other cases, however, had been worked out by Dr. Mac- 
Gregor, and, hence, I did not think it worth my while to do so. 
If, now, I combine my results with those obtained by him, I will, 
with the exception of the few sets mentioned above, have made. 
use of all available data. The mean values of m andi, as 
given by him, are 1.895 and 1.850 respectively and hence the 
values of m and 7 as given by averaging his mean values with 
mine are 1.913 and 1.851. 
The above result is in agreement with that reached by Prof. 
MacGregor by means of the second method referred to above 
The conclusion he arrived at was that, for all the eleotrolytes 
examined, the curves of his diagram were consistent with the 
depression constant having a common value of about 1.85. That 
the two methods should give results which are not only in close 
agreement with one another, but are also in close agreement with 
the value of the depression constant given by Van ’t Hoff’s 
theoretical expression for it, must be regarded as of considerable 
interest. 
