the compounds of chromium. 205 
As long as muriate of chromium is soluble in water it con- 
tains an excess of acid, varying from one half to one fourth 
of an atom according to the heat in which it has been dried. 
2. Nitrate of chromium. 
Nitric acid dissolves the hydrated oxide of chromium 
readily enough, if we assist the acid by the application of heat. 
The solution has a reddish blue colour, and always retains 
an excess of acid, what quantity soever of hydrated oxide we 
employ in the preparation. The solution is opaque, and if 
sufficiently diluted to be transparent, has a deep brownish 
purple colour by transmitted light. When evaporated to 
dryness it leaves a deep reddish blue matter, readily soluble 
in water, but not by any means so deliquescent as the 
muriate. A quantity of hydrate equivalent to 27*5 grains of 
green oxide was dissolved in nitric acid, and the solution 
evaporated to dryness. The residual matter was redissolved 
in water, and again evaporated to dryness. This process 
was repeated thrice. The weight of the dry salt was now 
69 grains ; its taste was acidulous, and very sweet, and the 
salt still reddened vegetable blues. The green oxide being 
thrown down by ammonia, and the liquid remaining evapo- 
rated to dryness, I obtained 33- 53 grains of nitrate of am- 
monia, equivalent to 22-63 grains of nitric acid. This would 
make the composition of the salt 
Nitric acid - - 22-63 or ~ atom. 
Green oxide - - 27-50 or 1 atom. 
Water - 18 87 or 3 atoms. 
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