the compounds of chromium. 203 
The greater number of them have a deep green colour ; 
though some of them are blue, and some of them purple. 
The intensity of the colour is such, that the aqueous solutions 
of most of them are opaque, even when dilute. They have 
a very strong and rather agreeable sweet taste, very often 
slightly acidulous, from the great difficulty of freeing them 
from all excess of acid. None of them can be crystallized ; 
but when evaporated to dryness, they assume the form of 
dark green, or nearly black powders. 
When the infusion of nutgalls is dropt into a solution of 
muriate of chromium a green flocky precipitate falls. 
Prussiate of potash occasions no precipitate, but when the 
mixture is heated it becomes dark brown and opaque, though 
no perceptible precipitate falls. 
Sulphuretted hydrogen occasions no precipitate, provided 
the salt of chromium be free from all traces of chromic acid; 
but hydrosulphuret of ammonia usually throws down green 
flocks, owing, I presume, to an excess of ammonia, which 
that hydrosulphuret frequently contains. 
Both carbonate of ammonia and caustic ammonia throw 
down the green oxide from muriate of chromium. But 
carbonate of ammonia does not answer for precipitating 
oxalate of chromium or acid phosphate of chromium, pro¬ 
bably because it forms compound salts with the acid and 
base. Caustic potash throws down the green oxide, but an 
excess of the alkali again dissolves the precipitate. 
When benzoate of potash is dropt into a concentrated 
solution of muriate of chromium, a green flocky precipitate 
falls, but no precipitate falls when the solution is dilute. 
