146 Mr. Children on Diaspore. fAve. 
Articte VIII. 
On Diaspore. By J.G. Children, Esq. FRS. &c. 
(To the Editor of the Annals of Philosophy.) 
DEAR SIR, British Museum, July 24, 1822. 
In the third volume (New Series) of the Annals of Philosophy, 
p- 433, Mr. G. B. Sowerby has published his discovery of a new 
variety of Diaspore, together with some experiments which I 
made, at his desire, on a portion of it by the blowpipe, and in 
the followmg volume, p. 17, your brother, Mr. W. Phillips, with 
his usual ability, has described the crystalline form of a similar 
substance in the possession of Mr. S. L. Kent, a fragment of 
which I have also examined, and am satisfied of its identity with 
the former. 
I have subsequently submitted the mineral to a further analy- 
sis, and, I believe, the results as stated below, are a pretty near 
approximation to. the: trath, though the quantity on which I 
operated was necessarily small, notwithstanding Mr. Sowerby’s 
liberality, who would willingly have furnished me with larger 
portions of this very rate substance, had I thought it right to 
consent to the sacrifice. 
The quantity of water was ascertained by heating the mineral 
to redness, in which operation pute water only was given off. 
The heated portion was fused with about eight times its weight 
of borax, the mass dissolved in’ diluted muriatic acid, and the 
whole precipitated by carbonate of potassa. The precipitate, 
well washed, was collected from the filter while in a moist state, 
and treated with.a solution of pure potassa, which left the oxide 
of iron untouched; and, lastly, the alumina was separated from 
the alkali by muriate of ammonia. 
The use of borax for the fusion of aluminous stones was, I 
believe, first recommended by Mr. Chenevix, and is the best 
flux for such minerals that I am acquainted with; but in the 
subsequent precipitation of the aluniina from its solution in the 
muriatic acid, by carbonate of potassa, it is necessary to concen- 
trate the solution by evaporation (for the glass requires a rather 
large quantity of fluid to dissolve it), or a considerable propor- 
‘tion will escape the action of the precipitant, even though boiled. 
{ was nearly led into a serious error by not being aware of this 
circumstance. 
It is stated, in Mr. Sowerby’s communication, that the test of 
boracic acid and iron before the blowpipe gave no trace of the 
presence of a phosphate in the mineral ; and I equally failed in 
detecting any, by treating a small portion with soda and silica, in 
