DETERMINATION OF FREEZING-POINT DEPRESSIONS, ETC. 423 
of it gave values of conductivity agreeing very well with those 
given by Kohlrausch.* 
Water. 
The water used, both in making up the solutions and in 
determining the freezing-point of water, was purified by boiling 
distilled water, containing a few grammes of barium hydroxide 
in a copper boiler and condensing it in a block-tin worm. It 
was kept in glass bottles, which had been used several years fcr 
that purpose. The conductivity of the water, obtained by ouce 
distilling, was never more than 1.25 x 107° at 18°C. expressed in 
Koblrausch’s new unit (ohm! em.!).- The determination of 
the conductivity was made by means of Kohlrausch’s method 
with the alternating current and telephone. The constant of the 
electrolytic cell used was determined by comparing the conduc- 
tivities of known solutions at 18° with those given by 
Kohlrausch.t I did not try to obtain water of a greater degree 
of purity, for the amount of any electrolyte present to give it 
this conductivity is so small that the freezing-point would not be 
affected in the fourth place of decimals. This I have deter- 
mined by using Kohlrausch’s§ table of conductivities, together 
with observations made on the freezing-point depressions of 
electrolytes of different observers. Of course theie is the possi- 
bility of a non-electrolyte being present, but we may safely 
assume that the amount of it present is, at least, not greater 
than that of the electrolyte, and even twice the amount of salt 
present, which would be necessary to give the above conduc- 
tivity, will not affect the freezing-point of water in the fourth 
place of decimals, 
Solutions. 
All solutions were made up at 0°C. The greater number of 
them were made by putting a known amount of the water- 
free salt in a 1000 ¢.¢. flask, and filling it up with water at 0°C. 
A few of the diluter solutions were made from these by means 
* Kohlrausch u. Holborn : Leitvermogen der Elektrolyte, 1898, p. 159, tab. 2. 
+ Kohlrausch u. Holborn: Leitvermogen der Elektrolyte, 1898, p. 1. 
t Loe. cit. 
§ Loc. cit. 
