54 



HYDRATES IN AQUEOUS SOLUTION. 



CALCIUM CHLORIDE. 



The data for calcium chloride are given in table 34. 



The freezing-point lowerings had already been determined, and a part of 

 the conductivity measurements made. The data necessary for calculating 

 the hydration in dilute solutions were partly lacking and these were obtained. 

 The value of fj.cc for calcium chloride, and for a number of the other salts 

 used in this work, was determined by Dr. West, to whom we wish to express 

 our thanks. 



From column m' it will be seen that the amount of water that has entered 

 into combination increases with the concentration of the solution. This 

 is just what we should expect from the law of mass action. The larger the 

 amount of the salt present, the greater the amount of water that would be 

 held in combination. The slight increase in the amount of water combined 

 as we pass from 0.153 normal to 0.102 normal is to be noted, because a 

 similar phenomenon occurs in other cases. 



If we turn our attention to the number of molecules of water combined 

 with one molecule of the dissolved substance, we shall see that this increases 

 from the most concentrated solution to about half-normal, and then, with 

 considerable fluctuation, does not change in any decided manner. The 

 number of molecules of water in combination with one molecule of the dis- 

 solved substance is really of less interest and importance than the total 

 amount of water held in combination by the dissolved substance; the latter 

 has therefore been plotted in the curve against the concentrations as 

 abscissae. The curve shows, at a glance, that the amount of water held in 

 combination increases, and fairly regularly, with the concentration. 



TABLE 34. CALCIUM CHLORIDE. 



