332 Dr. W. A. Tilden and Mr. W. A. Shenstone. [May 7 r 



Fig. 1. 



In the experiments made at lower temperatures the solutions were 

 placed together with excess of pure calcium sulphate in stoppered 

 "bottles or flasks, which were immersed in the bath maintained at a 

 constant temperature for at least five hours with constant agitation. 

 At temperatures above 20° a special contrivance was used for filtering 

 off the solution required for analysis without change of temperature 

 or evaporation. 



All the materials employed were pure, and filters purified by acid 

 were alone used. 



Two series of determinations have been made, the first with a solu- 

 tion containing a fixed proportion of chloride at different temperatures r 

 and the second at constant temperature with a varying strength of 

 solution. 



These results are indicated graphically on the accompanying diagram 

 (fig. 2), from which it will be observed that whilst the solubility 

 of calcium sulphate in water is increased by the addition of chloride 

 of sodium or of ammonium, probably owing to double decomposition, 

 it is diminished by the presence of chloride of calcium. It may also 

 be noticed, however, that the form of the curve is nearly the same in 



