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 cm. long, 

 with an internal diameter of 3.3 cm. 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. 

 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 cm. 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 



