18 ROYAL SOCIETY OF CANADA 
produced in dilute solutions by all molecules, whatever the substance and 
whether they are undissuciated molecules or free ions, is the same. On 
the assumption that the depression constants for undissociated molecules 
and for free ions are the same for all electrolytes, we may use the above 
determinations to get still closer values of them. For some of the errors 
involved in the determination of the k’s and the /’s are quite as likely to 
be positive as negative. The straight lines drawn in to represent the 
experimental curves in their most dilute portions are as likely to be too 
high as too low and to have too great an inclination to the depression 
axis as to be too slightly inclined to it. Errors due to the impurity of 
the water, the ionization of the water itself, and the use of electrically 
determined ionization coefficients may or may not be thus variable in 
sign. But as the former sources of error are probably the main ones, 
the average values of the respective depression constants of the above 
table will give a closer approximation to the true common values, if there 
are common values, than the individual determinations. Taking the 
averages we find the depression constant for undissociated molecules to 
be 1-895 and that for free ions to be 1-850. 
On the additional assumption that the depression constants for 
undissociated molecules and for free ions are the same, the common value 
would be that found for the latter, as being affected by the smaller error. 
That the depression constant, assumed the same for undissociated 
molecules and for free ions, as well as for all electrolytes, should thus 
be found to have the value 1°85 is of interest, because it is expected to be 
found to have approximately this value both on theoretical grounds and 
because of the results of observations on non-electrolytes. It is of 
interest, however, rather as indicating the value of the method used 
above than because of the value of the result. If thoroughly treated the 
above observations would give a somewhat different result ; for in finding 
the average value of the constants we have regarded all the individual 
determinations as having the same weight. Obviously they are of different 
weights. It is hardly worth while to endeavour to estimate their relative 
trustworthiness, because in an investigation intended to give a close 
determination of the depression constant by the method used above, 
it would be necessary to take into account the whole body of our 
knowledge of the depression of the freezing-point by electrolytes. 
The result is of interest, however, as showing that the method used 
above gives us a means of handling the bewildering multiplicity of 
observations which have been accumulated in this department of 
experimental investigation. It has been found practically impossible to 
get at values of the depression constants for different electrolytes, and 
consequently to determine what its value is on the assumption that it 
has a common yalue, by carrying observations to extreme dilution, 
because of the percentage error to which such observations are 
