244 W. Gibbs and F. A. Genth 
freshly prepared sesquioxyd of cobalt, and the whole allowed to 
stand for several weeks, after which time it was boiled with 
chlorhydric acid, and considerable quantities of chlorid of Pur- 
pureocobalt, Luteocobalt, and Praseocobalt, were obtained. This 
experiment leaves no doubt that the ammonia-cobalt bases can 
be prepared by the direct action of ammonia upon sesquioxyd 
of cobalt, though this mode of preparation is not economical. 
The chlorid of Roseocobalt may also be prepared by adding 
cold and strong chlorhydric acid to a completely oxydized solu- 
tion of the ammoniacal nitrate or sulphate of cobalt. A brick- 
red precipitate is formed in either case, which must be purified 
by repeated washing with chlorhydric acid. Strong chlorhydrie 
acid also precipitates the chlorid from solutions of the sulphate 
and nitrate of Roseocobalt. In all these cases, however, it is 
difficult to obtain the chlorid in a perfectly pure state. 
The chlorid of Roseocobalt is usually precipitated as a brick- 
red powder, which, under the microscope, appears to be com- 
posed of indistinct granular crystals. It may be purified, though 
portion of chlorid of Roseocobalt into chlorid of Purpureocobalt, 
as may easily be observed by the change of color. This trans- 
formation is, however, far more striking when a solution of chlo- 
rid of Roseocobalt is boiled with a little chlorhydric acid: the 
ef to a beautiful 
: 5NH:3.Co2Cls. 
This differs from that of the chlorid of Roseocobalt only by con 
taining no water of crystallization. The change which takes 
place in the conversion of one chlorid into the other does not 
f 
