14 



PROCEEDINGS OP THE AMERICAN ACADEMY. 



The Extraction of the Green Solution with 

 Alcohol and Ethek. 



No. of times -itt • v^ r 



boiled and ^?'S^* °^ 



extracted. 



2 

 3 

 5 

 6 

 9 



14 



12 



Cr,0,. 



0.1408 

 0.1407 

 0.1034 



0.3981 

 0.0724 

 0.1571 

 0.0474 

 0.0669 

 ( 0.0322 

 I 0.0321 



Weight of 

 BaSO,. 



0.0760 ; 

 0.0760 ' 



0.2272 

 0.2261 



Atomic Ratio 



2.52 

 2.52 



2.46 

 2.41 

 2.25 

 2.06 



[1.52] 



1.98 



1.94 



Distribution between two Solvents. 

 In 1863 Siewert endeavoured to distinguish between the acid and 

 basic salt by distributing the two substances between two solvents, in 

 which it was reasonable to suppose that the two would have different 

 solubilities. He treated an aqueous solution with a mixture of ether 

 and alcohol for this purpose, and found that the viscous aqueous solution 

 remaining was basic, containing only about 2.4 SO4 instead of 3 SO4 for 

 each Crj. In the light of the facts described above, it seemed to us pos- 

 sible that this basic substance was mixed with some unchanged chromic 

 sulphate ; because there is no proof that the hydrolysis was complete in 

 the presence of the acid, and several reasons for believing that it was not 

 complete. This inference could be tested by boiling the green viscous 

 residue with water after its acid had been removed. If the compound 

 had been hydrolyzed as much as possible, further extraction with alcohol 

 and ether could have no further effect; but if the hydrolysis were incom- 



