302 



Conductivity of Aqueous Solutions. Part X. 



Since the determinations of solubility were to be made by measuring 

 the conductance of the saturated solution in the presence of an excess 

 of solid salt, the question arose whether the latter would influence the 

 conductance-capacity appreciably, as it might possibly do by settling 

 out upon the cylindrical electrode or even by remaining in suspension. 

 To answer this question, a 0.01 normal sodium chloride solution was 

 measured in the bomb both at 18 and 100, first alone and then in the 

 presence of 0.5 to 0.8 c.cm. (measured moist) of solid silver chloride. 

 The conductance of the dissolved portion of the latter salt can be shown 

 by applying the principle of the common-ion effect to the solubility-value 

 hereinafter presented (152 X 10" 6 mols per liter at 100) to be only about 

 1 X10~ 6 reciprocal ohms even at 100, and therefore to be negligible in 

 comparison with the conductance of the sodium chloride. The specific 

 conductances multiplied by 10 6 observed in these experiments are given 

 in the following table. 



*These second and third values were obtained by removing the bomb from the bath, shaking 

 it, returning it, and allowing it to come to the original temperature. 



These results show that the effect of the solid salt on the conductance 

 certainly does not exceed 0.4 per cent and it is not improbable that the 

 differences of this magnitude observed at 18 were due to temperature 

 variations, which were not entirely excluded in these first experiments ; 

 for the differences at 99.8 where the temperature regulation was auto- 

 matic seem to be scarcely appreciable. In any case the effect of the solid 

 salt on the conductance-capacity is less than the other errors of the solu- 

 bility determinations. 



The correction for the conductance of the water, which is important 

 in such dilute solutions, was determined as follows, in order to avoid 

 making a new measurement in the bomb at 100 with each new sample 

 of water. Each of two separate samples was measured nearly simulta- 

 neously at 46 in the glass apparatus with un-platinized electrodes which 

 I had previously used for solubility experiments* and at 100 in the 

 bomb itself after it had been thoroughly soaked out by heating with pure 

 water at 100. 



*Z. phys. Chem., 46, 530 (1903). 



