4 Messrs Paine and Evans, The Conductivity of 4 
solutions, two conductivity cells were used. The one cell (Fig. 2) 
was of ordinary glass, and had been in use for some years pre- 
viously for testing distilled water. Some of the earlier acid solutions 
Fig. 2. Fig. 3. 
were measured in this. The second cell (Fig. 3) was made of 
Jena glass. Some of the acid solutions and all the alkali ones: 
were measured in this cell. In the case of the acid solutions, the 
results for the two cells agreed closely, so that the solvent action — 
on the ordinary glass walls of the former cell was of no conse- | 
quence for the time the solutions remained in the cell. The | 
electrodes in both cells had been platinised and heated to redness © 
before being sealed into the glass. Contact with the electrodes » 
was made by means of mercury poured into the side tubes. 
The cell constants were determined by means of a standard | 
potassium chloride solution, the conductivity of which was deduced | 
from Kohlrausch’s Tables. The resistances in all cases were 
measured by means of the Wheatstone’s Bridge method, using the | 
double commutator and galvanometer. The cells were maintained | 
at 18° C. in a well-stirred water bath. 
The water used for all the measurements, and also for making — 
up the solutions, had been redistilled in a Jena glass apparatus — 
(of 6 litre capacity) with a little potassium dichromate and — 
sulphuric acid. The distilling flask was placed in a fume chamber, 
