312 Mr. Hatchett's Analysis of 
The undissolved residuum of the nitric solution was then 
boiled with lixivium of pot-ash, which was afterwards satu- 
rated with muriatic acid, and became tinged with blue when 
prussiate of pot-ash was added. 
The residuum was now a black powder, which was edul- 
corated, and was immediately dissolved when nitric acid was 
poured on it ; at the same time nitrous fumes were emitted. 
The solution was transparent, excepting that a few white par- 
ticles were floating in it. 
It was then diluted, and filtrated. 
Prussiate of pot-ash turned it to a brownish-green, which 
afterwards became brown. Lixivium of pot-ash precipitated 
a white flocculent matter ; and caustic ammoniac, added to a 
third portion, precipitated a quantity of iron. 
As this precipitate had some remarkable properties, parti- 
cularly in respect to the difficulty with which it was de- 
composed, I have been induced to mention the experiments 
made on it in a circumstantial manner. 
This precipitate appears from these experiments to be prin- 
cipally composed of iron, and some molybdic acid, together 
with a small portion of alkali and sulphuric acid. - 
The intimate union between the iron and molybdic acfJ is 
apparently the cause which impedes the decomposition of this 
precipitate ; but this can only be ascertained by future expe- 
riments on molybdate of iron. 
I next examined the white precipitate which was deposited 
by the last evaporations, and found that (when distilled with 
nitric acid) it was converted into the yellow molybdic acid; 
and I was therefore convinced that this last portion of the 
