﻿and the Solvate Theory of Solution. 733 



as yet largely unpublished in any scientific journal *. A 

 careful study was made of the absorption spectra of cobalt 

 salts in different solvents as affected by temperature. Glycerol 

 solutions of these salts showed a different spectrum from 

 aqueous solutions, indicating the presence of glycerolates in 

 such solutions, as we have hydrates in aqueous solutions. 



The effect of rise in temperature is to increaso enormously 

 the absorption of concentrated aqueous solutions of cobalt 

 chloride, especially in the red. It is well known that such 

 solutions turn blue on heating. The more concentrated the 

 solution the lower the temperature at which this colour 

 change takes place. There is a large amount of evidence 

 which points to the conclusion that the change in absorp- 

 tion is due to a breaking down of the more complex 

 hydrates with rise in temperature. If this is the true expla- 

 nation of the phenomenon, the presence of a dehydrating 

 agent such as calcium chloride or aluminium chloride ought 

 to cause this change in absorption to take place at a lower 

 temperature, since the dehydrating agent would assist the 

 rise in temperature in breaking down the complex hydrates. 



The results here are in accord with prediction. The 

 addition of either of the above chlorides causes the great 

 absorption in the red to take place in more dilute solutions 

 at the same temperature, or in a given solution at a lower 

 temperature. 



It was further found that the temperature at which this 

 marked change in the red absorption takes place is higher for 

 aqueous and glycerol solutions than for solutions in other 

 solvents ; showing that the u hydrates " and " glycerolates " 

 are more stable with respect to temperature than other 

 solvates. 



The effect of rise in temperature on salts of chromium was 

 also studied, and was shown to be similar to the effect of rise 

 iii temperature on cobalt salts — the higher the temperature 

 the greater the absorption. 



The action of dehydrating agents on chromium salts was 

 similar to that on salts of cobalt. 



Absorption Spectra of Uranium Salts. 



A fairly comprehensive study was made of the absorption 

 spectra of uranium salts, to see especially whether there was 

 evidence obtainable for the existence of definite solvate bands 

 in different solvents. We studied both uranyl and urunous 

 compounds. 



* See Carnegie Institution of Washington, Publications 130 and 160, 



