ELISHA MITCHELL SCIENTIFIC SOCIETY. 13 
seen that they agree in part only with the observations 
just quoted. 
Action on the Violet Solution.—W hen alcohol was ad- 
ded to the violet solution of alum, fine violet crystals were 
precipitated, which gave on analysis the following re- 
sults: 
Calculated for Found. 
KoCre(SO4)4.12H:O. r Fi; 
oe ee eee 13.32 13.68 13.36 
ee aN ai Read ay 9.99 9.80 
Sg oe ss os 49.99 48.85 
This may be an old observation that on Supatantitite 
from alcohol the, crystals contain only half the usual 
amount of water, but we have not met with it anywhere. 
The fact that this very considerable change of hydration 
effects no change in color nor in the precipitating power 
of barium chloride, argues against the partial dehydra- 
tion theory of Schrétter and Etard. It should be added 
that the precipitation was carried out with absolute alco- 
hol upon concentrated solutions of the alum, was rapid, 
and the precipitate was immediately removed. There 
seemed to be two layers of crystals, one ef violet crystals 
(upper) and the othera heliotrope powder. Analysis show- 
ed that the cemposition of both was the same and that 
the difference was probably oneof subdivision. The pre- 
cipitation is almost complete, as the alcohol shows very 
little color. From this it is evident that alcohol itself 
does not materially affect the violet solutions. 
Action on the Green Solutions.—Green ee of 
the alum were first experimented with. When absolute 
alcohol is added to concentrated solutions of chrome alum, 
which have been boiled until green and allowed to cool, a 
dark green gummy mass separates out after a short time. 
If the boiling is not sufficiently prolonged there will form 
afterwards a few violet crystals. The alcohol retains 
something in solution, as is shown by the green color. 
This amount retained may be considerable if much water 
