36 IONIZATION COEFFICIENTS OF CERTAIN 
was found to occur on preparing the most concentrated mixture 
examined, which would appreciably affect its concentration with 
respect to the two electrolytes, when calculated on the assumption 
that no such change of volume occurred. 
Method of Measuring Conductivity. 
The method used was Kohlrausch’s Telephone method, and 
the apparatus was the same as described in the paper just 
referred to. 
Two electrolytic cells were used, one for strong, the other for 
more dilute solutions. The first was U-shaped of the form 
shown by. Ostwald in his Physico-Chemical Measurements, page 
226, Fig. 178. The second was cylindrical, about 14 em. long, 
with an internal diameter of 3.3 em. It was provided with 
circular electrodes of stout platinum foil not easily bent. The 
stout wire supports of these electrodes were fused into glass 
tubes which passed through, and were sealed to, the ebonite 
cover of the cell. The electrodes were kept firmly in position by 
means of a rubber band passing over the cover and around the 
bottom of the cell. This cell being long and of the same 
diameter throughout, could, by variation of the distance between 
the electrodes, be used for solutions extending through a wide 
range of dilution. 
The platinizing of the electrodes was carried out as described 
in the paper cited above. 
The water-bath described in the above paper was used for 
these experiments also, modified, however, when working at 0° C, 
as follows :—A cylindrical screen made of wire gauze about 15 
cm. in diameter was hung from a support so as to reach from the 
top, to within 6 or 8 em. of the bottom, of the bath. Inside 
this, the electrolytic cell containing the solution to be measured, 
was placed, while outside was a mixture of snow and a very 
little sodium chloride. The screen thus prevented the snow 
from coming into contact with the cell, while the water around 
it could be thoroughly stirred. By varying the amount of salt 
the temperature could be kept within a twentieth of a degree of 
