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 for 

 that purpose. The conductivity of the water, obtained by once 

 distilling, was never more than 1.25 x 10~" at 18C. expressed in 

 Kohlrausch's new unit (ohm~ l cm." 1 ).-!- The determination of 

 the conductivity was ir-ade 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.J 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 0C. The greater number of 

 them were made by putting a known amount of the water- 

 free salt in a 1000 c. c. flask, and tilling it up with water at 0C. 

 A few of the diluter solutions were made from these by means 



Kohlrausch u. Holborn : Leitvertnogen der Elektrolyte, 1898, p. 159, tab. 2. 

 t Kohlrausch u. Holborn : Loitveruiogen der Elektrolyte, 1898, p. 1. 

 I Loc. cit. 

 i Loc. cit. 



