1902 - 3 .] Freezing-Point Depression in Electrolytic Solutions. 377 
Except in the case of sodium chloride it will be seen that here 
there are great divergences between the ionisation values calculated 
from cryoscopic and electrical observations. The error of the 
freezing points can scarcely amount to a unit in the second decimal. 
The error in the conductivities is much smaller than this, so that 
we are obliged to conclude that the two methods lead to essentially 
different results in the case of hydrochloric acid and potassium 
chloride. It is true that, owing to the uncertainty in the 
maximum molecular conductivity of all acids, the electrical 
ionisation value for hydrochloric acid is affected by a greater error 
than the corresponding numbers for the neutral chlorides, hut the 
divergence from the cryoscopic value is much too great to be 
accounted for in this way. It might be urged that, as we have 
taken acetic acid as our standard of reference, the differences 
might arise from some peculiarity in the behaviour of this substance. 
When we consider, however, that we obtain correct values for the 
ionisation of malonic acid by the use of the same method, it must 
be conceded that such an objection loses much of its force. 
Again, we find, in accordance with other observers, that by the 
cryoscopic method sodium chloride appears to be less highly 
ionised than potassium chloride, whereas by the conductivity 
method the reverse is apparently the case. Here, if the standard 
substance is merely uniform in its behaviour, whatever be its 
peculiarities in other respects, we have a well-marked divergence 
between the cryoscopic and electrical methods. 
Equivalent Depression for Acetic Acid. 
The following table shows the depressions actually observed for 
approximately decinormal solutions of acetic acid under the 
conditions prevailing on different days, and for the purpose of 
comparison a column has been added which gives the values for 
accurately decinormal solutions calculated by means of Blagden’s 
law from the two columns immediately preceding it. This table, 
like all others in this paper, gives the depressions as they were 
obtained directly from the thermometer, no corrections of any 
kind, except calibration corrections, having been applied. 
PROC. ROY. SOC. EDIN. — YOL. XXIV. 
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