Experimenis on Allanite. “287 
the strong heat to which I had subjected it: whereas the 
oxide of cerium from cerite had been examined in the state 
of carbonate. 
7. In the many experiments made upon this powder, 
and upon oxide of cerium from cerite, I repeated every 
thing that had been established by Berzelius and Hisinger, 
Klaproth and Vauquelin, and had an opporiunity of ob- 
serving many particulars which they have not noticed. It 
may be worth while, therefore, without repeating the de- 
tails of these chemists, to mention a few circumstances, 
which will be found useful in examining this hitherto scarce 
oxide. 
a. The precipitate occasioned by oxalate of ammonia is 
at first in white flocks, not unlike that of muriate of silver, 
but it soon assumes a palverulent form. It dissolves readily 
in nitric acid, without the assistance of heat. The same 
remark applies to the precipitate thrown down by tartrate 
of potash. But tartrate of cerium is much more soluble in 
acids than the oxalate. 
b. The solution of cerium in acetic acid is precipitated 
gray by infusion of nut-galls. Cerium is precipitated like- 
wise by the same re-agent from other acids, provided the 
solution contain no excess of acid. This fact was first ob- 
served by Dr. Wollaston, who communicated it to me last 
summer. I immediately repeated his experiments with 
success. 
ce. Cerium is not precipitated from its solution in acids 
by a plate of zinc. In some cases, indeed, I have obtained 
a yellowish-red powder, which was thrown down very 
slowly. But it proved, on examination, to consist almost 
entirely of red oxide of iron, and of course only appeared 
when the solution of cerium was contaminated with iron. 
d. The solutions of cerium in acids have an astringent 
taste, with a perceptible sweetness, which however is dif- 
ferent from the sweetness which some of the solutions of 
iron in acids possess. 
e. The muriate and sulphate of cerium readily crystallize; 
but I could not succeed in obtaining crystals of nitrate of 
cerium. 
J. The best way of obtaining pure oxide of cerium js 
to precipitate the solution by oxalate of ammonia, wash 
the precipitate well, and expose it to a red heat. The 
powder obtained by this process is always red ; but it varies 
very much in its shade, and its beauty, according to cir- 
cumstances. This powder always contains carbonic acid. 
8. 1 consider the following as the essential characters of 
cerium, 
