322 ON THE CALCULATION OF THE CONDUCTIVITY OF 



tions. The method of procedure in calculation will be more 

 exactly described after the experimental determinations have 



been dealt with. 



To obtain the experimental data required in the calculation, 

 it is necessary to make up a long series of solutions of each salt 

 and measure their conductivity. The volumes of the constituent 

 solutions before mixing must be known, and in cases where there 

 is an appreciable change of volume on mixing the densities of 

 the single solutions and of the mixture must be found. These 

 determinations will be taken up in order. 



Purity of Salts. 



Of the salts used the sodium chloride had been furnished 

 by Merck, the barium chloride by Eimer & Amend of New 

 York. The former was tested for metals of the alkali and 

 alkaline earth groups, as well as for iron. No indication of 

 these was found. The barium chloride was tested by heating 

 in a Bunsen flame. No impurities were discovered in this way. 

 A further indication that the salts were sufficiently pure for 

 the purpose in view is given by the comparison of the conduc- 

 tivities with those of Kohlrausch, as shown farther on in the 

 paper. All the salt, however, used in the experiments described 

 here, was recrystallized once by the writer. 



Purity of Water. 



The water used in making up the solutions was obtained by 

 adding potassium hydroxide, about 1 gramme to a litre, to ordi- 

 nary distilled water, and redistilling by means of a copper boiler 

 lined with tin, the distillate being collected in a block-tin worm. 

 The conductivity of the water before the potassium hydroxide 

 was added was about 1.87 in terms of the conductivity of 

 mercury at 0CxlO~ 10 . After distillation the conductivity 

 ranged from 1.1 to 0.95, the latter being that of the water used 

 for the very dilute solutions. 



At an earlier stage of the experiments water was purified by 

 methods derived from a paper by G. A. Hulett.* Instead of the 



* Journal of Physical Chemistry, Vol. I, No. 2. 



