[BARNES ] DEPRESSION OF THE FREEZING-POINT 39 
MATERIALS. 
Both the hydrochloric and sulphuric acids were obtained from Merck. 
It was found that solutions of them had conductivity values showing 
satisfactory agreement with the values as given by Kohlrausch,' and they 
were thus considered sufficiently pure for the purpose. 
The water used in making the solutions was purified by boiling 
ordinary distilled water with a few grammes of barium hydroxide in a 
copper boiler lined with tin, and condensing ina block tin worm. The 
first 200 cc. that came off was always thrown away. The water thus 
purified had at 18° C. a conductivity of about 0°95 x 10° expressed in 
Kohlrausch’s new unit’ (ohm cm.”). 
The amount of hydrochloric or sulphuric acid in a solution was de- 
termined volumetrically by means of a standardized solution of potassium 
hydroxide with phenol-phthalein as indicator. All burettes and pipettes 
used in the preparation and analysis of these solutions were calibrated by 
the weight of distilled water they delivered, and the flasks by the weight 
of water they held at 0° C. 
MEASUREMENT OF CONDUCTIVITY. 
L] 
Conductivities were determined by Kohlrausch’s method with the 
alternating current and telephone. The coils of the Wheatstone’s bridge 
were certified to be correct at 17:5° C. to one-fiftieth of one per cent and 
to have a temperature coefficient of 0:000267 per centigrade degree per 
ohm. The correction for temperature was applied when the observations 
were made at temperatures appreciably different from 17°5°. The plati- 
noid bridge wire was calibrated by the method proposed by Strouhal and 
Barus* with ten german-silver wires of equal length. A telephone made 
by Ericsson of Stockholm, and an inductorium made after a plan of Ost- 
wald’s, and giving a clear high note, were employed. 
Two types of electrolytic cell were used. One, with the shape of a 
U-tube, was employed for the stronger solutions. The other, of the Ar- 
rhenius form, was used for the weak solutions employed in the determina- 
tion of the specific molecular conductivity at infinite dilution for 0° C. 
The electrodes were all of stout platinum foil, firmly fixed to the platinum 
wire or glass connections, so that the capacity ofthe cell once determined 
would remain the same throughout a series of experiments. These elec- 
trodes were platinized in a solution prepared from Lummer and Kurl- 
baum’ s‘recipe. The reduction factor of each of these cells, by which 


1 Kohlrausch u. M bé - een dés Hleitnoly tas 1898, p. 160, tab. 2 
2 Ibid, p. 1. 
3 Wied. Ann., 10, 326, 1880. 
4 Wied. Ann., 60, 315, 1897. 
