514 PROCEEDINGS OF THE AMERICAN ACADEMY. 



We determined also the solubility of both the dihydrate and the tetra- 

 hydrate of the double sulphate of manganese and potassium, and found 

 solutions saturated at 25.0° with both or either hydrate to yield 40.1 grams 

 of anhydrous solid. Hence this temperature must be near the transition 

 temperature of the two hydrates. The detailed publication of these 

 results and many other similar observations must be reserved for a later 

 communication. 



In a few words of recapitulation, the present paper may be said to 

 confirm the work of Cottrell and to disprove that of Linebarger, while 

 a measure of doubt is cast upon the usual methods of determining 

 solubility. 



Cambridge, February, 1901. 



