1902 - 3 .] Freezing-Point Depression in Electrolytic Solutions. 367 
was tied by means of cotton thread over the widened end of the 
filter tube. 
The thermometer was attached above C to the stage of a micro- 
scope used for accurately reading the position of the mercury on 
the scale. The microscope with the thermometer was movable 
vertically on a stand, fine adjustments for reading being made 
with the screws of the microscope stage. The hammer of an 
electric bell, covered with chamois leather, was fitted for tapping 
the thermometer (compare Barnes, Trans. Roy. 
Soc., Canada, vol. vi. p. 37). 
In order to obtain ionisation values for a 
strong electrolyte, our intention was to make 
on the same day two experiments, one with 
a non-electrolyte, the other with a strong electro- 
lyte, the freezing-point depression being made 
as nearly as possible the same in the two cases. 
From the concentration of the two solutions it 
would then be possible to calculate the ionisa- 
tion value of the strong electrolyte, due allow- 
ance being made for the small difference in 
the freezing-point depression according to Blag- 
den’s law. Since, however, the accurate analyt- 
ical estimation of a suitable non-electrolyte w T as 
found to be a matter of considerable difficulty, 
we chose instead acetic acid, which is very feebly 
ionised, and whose small ionisation values are 
accurately known. Our day’s work finally re- 
solved itself into determining the freezing-point 
depression and equilibrium concentration of an 
approximately decinormal solution of acetic acid, 
and immediately thereafter the same magnitudes for a solution of 
a good electrolyte of approximately the same freezing point. 
We first charged the Dewar vessel with 80 c.c. of distilled water 
cooled to 0°, and thereafter added 45 grams of freshly-planed ice 
made from distilled water. This ice was, of course, a wet mass, 
but the quantity of dry ice it contained could be estimated from 
the final concentration of the solution in the manner to be after- 
wards described. The stopper, with stirrer and filter attached, 
