Dissociating Powers of Free and of Combined Water. 



165 



ductivities of these solutions were now determined. These were not 

 the sum of the specific conductivities of the two salts present in each 

 case, but were less, because of the common ion effect. But since the 

 two solutions contain the same number of ions (the added salt not being 

 considered), the driving back of the dissociation of the added salt by 

 the anions would be the same in each case. When the conductivity of 

 a solution, say, normal with respect to potassium chloride and half 

 normal with respect to magnesium chloride, had been measured, the 

 cell was thoroughly cleaned and dried. This same cell was now used 

 for the determination of the conductivity of a solution 0.6951 normal 

 with respect to calcium chloride, that is, isochloric, and half-normal as 

 regards magnesium chloride. Thus the possibility of error due to any 

 change in the cell was eliminated. 



Three concentrations of the added salt were used, first in solutions 

 normal for potassium chloride and then in solutions 0.6957 normal for 

 calcium chloride. The increase in conductivity due to the added salt 

 was calculated in each case. The difference of the increases for com- 

 parable solutions was then computed. 



The numbers given here for conductivities represent the mean of 

 three readings of the bridge for different resistances. 



TABLE 95. 



Normal for KC1. 



0.6951 normal for CaCl 2 . 



