on the Ammonia-cobalt Bases. 261 
which a little chlorhydric acid has been added, and filtered. On 
cooling, the chlorid of ureocobalt izes in small b 
liant crystals, which must be repeatedly recrystallized to separate 
all traces of impurity. The washings, on boilmg with chlorhy- 
dric acid, yinld: a fresh portion of the chlorid. The reaction 
which takes place under these circumstances may be expressed 
by the equation 
NOz.5NH3.CosO0s, 2NOs +3HClI=NO2+2NOs, HO+ 
: 5NHs.Co2Cls+HO. 
As already remarked, the chlorid or sulphate of Xanthocobalt 
may be employed in a precisely similar manner, and also yield 
the chlorid of urpureocobalt, en the sulphate is used, how- 
ever, the resulting chlorid is apt to retain sul hurie acid with 
much obstinacy, and can with difficulty be freed from it. 
Another method of preparing the chlorid of Purpureocobalt, 
consists in boiling the chlorid or nitrate of Roseocobalt with 
chlorhydric acid. This method is very convenient, and yields 
avery pure chlorid. 
_ The chlorid of Purpureocobalt may also be prepared by boil- 
ing the acid sulphate of this base with chlorhydric acid. In 
this case, however, as in all others in which sulphuric acid is 
Present in the solution, the chlorid should be boiled with a little 
chlorid of barium, and repeatedly recrystallized, to separate 
traces of the isomorphous sulphate of Roseocobalt formed at the 
Same time. 
. 
- 
tion 
is soluble without decompositi r to which a i 
drops of chlorhydric get have been added. From this gate 
It separates, on cooling, in very brilliant small crystals, whic 
are simpler in form, the purer the solution from which they have 
crystallized. The crystals belong to the square atic te 
dimetric system, according to Prof. Dana, and not to the regular 
stem, as stated in previous memoirs. The observed ties are 
the octahedron and first and second prism. P.aPa.Pa. 
€ angles in Dana’s notation are (see fig, 1) : ss 
Pre = as yt ink csaep: As] (calonlated 107° 12°). 
3 seated) = laate 
li: i oe the bg aan? over the top = 85°. 
e€ usually small but extremely well formed ; 
those which are obtained. froth solutions containing a little chlo- 
nid of mercury most frequently exhibit the planes of the first 
