24 PROCEEDINGS OF THE AMERICAN ACADEMY. 



solutions. When the solution is saturated at 100'^ with chromic hy- 

 droxide, a mixture containing the same amount of chromium per litre''as 

 before causes a depression of the freezing point of only 0.080°, and a 

 parallel mixture saturated at 20^^ with chromic hydroxide causes a depres- 

 sion of only 0.071°, instead of 0.30° found at first.* 



This decrease in the depression of the freezing point indicates a 

 decrease in the number of dissolved particles, the final value correspond- 

 ing to only 1.5 particles for every four chromium atoms. These results 

 are only preliminary ones ; they will be repeated and amplified in the 

 near future. As far as they have any significance, they seem to indicate 

 that one of the green bodies really possesses a high molecular weight, as 

 Recoura and Whitney believed, although at least one of these bodies is 

 more basic than these investigators assumed. 



Chkmical Retardation of thk FIydrolysis. 



The preceding experimentation is unanimous in indicating that at least 

 one soluble green basic substance is found by the hydrolysis of violet 

 chromic salts, and that the extent, and of course also the speed, of this 

 hydrolysis is dependent upon the temperature. 



If this is true, the neutralization of the acid formed by hydrolysis 

 should greatly favor the formation of the basic substance, while on the 

 other hand the addition of more acid siiould retard this formation. Tiie 

 former of these consequences has already been shown to hold true — it 

 introduces an accidental circumstance into the work of both Whitney and 

 Recoura. The latter of the consequences remains to be proved. 



With this object freshly prepared solutions of the violet and merely 

 boiled green solution, of one-fortieth molar strength, were each divided 

 between four test-tubes, every tube containing ten cubic centimeters. 

 To one test-tube of each color was added a gram of ammonic chloride, to 

 another of each color a gram of sodic sulphate, and to a third of each 

 color a gram of sulphuric acid, while the fourth of each color was left 

 unmixed. Each was slightly diluted until all were equal in volume. All 

 were allowed to stand together in the laboratory at temperatures varying 

 from 20° to 27°. At the end of a week the green and violet tubes were 

 distinctly less different than at first, and in each series the test-tube con- 

 taining excess of acid was unquestionably the most violet. The sodic 

 sulphate seemed very slightly, and the ammonic chloride somewhat more 



* The actual depressions measured were respectively 0.053° and 0.108° for 

 solutions yielding 0.0503 and 115G Cr._,0;j per 10 c.c. respectively. 



