the Arseniates of Copper , and of Iron. 225 
effected in a bottle well stopped, and defended from the contact 
of the atmosphere, no change of colour took place ; and that 
portion which was dissolved by an excess of ammonia remained 
in the solution. In endeavouring to distil, or to evaporate, the 
water of this colourless solution, in order to bbtain crystals, it 
became of a light green, the intensity of which augmented, as 
the distillation was continued. I could not, therefore, hope to 
procure this salt in a crystalline form. Hence, it is evident, 
that we have a white muriate of iron, which, as well as the 
oxide it contains, is very susceptible of assuming an addition of 
oxygen ; for, to that alone I attribute the precipitation caused in 
a solution of that salt, into which the different reagents above- 
mentioned had been poured ; a precipitation which did not take 
place, till after it had been exposed in a situation where it could 
absorb the quantity of oxygen necessary to produce a change in 
its principles. 
This solution of white muriate of iron, when exposed to the 
air, becomes green, and is then in the state of green muriate, well 
known. At a certain degree of oxidation, I have observed the 
precipitate formed, to be soluble in the carbonates of potash and 
of soda, and still more so in that of ammonia ; but, upon ab- 
sorption of oxygen, to be quickly abandoned by them, and then 
to fall to the bottom, in a blackish powder mixed with yellow. 
If, into a solution of green muriate of iron, nitric acid is poured, 
both liquors being cool, and not too concentrate, the muriate 
will become of a blackish brown, not unlike malate of iron. 
Precipitated by the alkalis, it yields a black powder, no longer 
soluble in them ; but which resembles, in every respec t, com- 
mon black oxide of iron. 
If this green muriate of iron is further exposed to the air, 
mdccci. G g 
