ON THE COMPOSITION OF JAMEs' POWDER. 153 
of the Philosophical Transactions, first published a series of 
experiments which he had undertaken with a view to deter- 
mine this point. Mr. Chenevix, in the Philosophical Tran- 
sactions for 1801, also made known some observations on this 
substance. Berzelius, in his Lehrbuch, casually notices some 
experiments made by himself on a portion of James' powder; 
and lastly Mr. Richard Phillips, in the twentieth volume of 
the Annals of Philosophy, gives an account of the composi- 
tion of the pulvis antimonialis of the Pharmacopoeia. 
Dr. Pearson's analysis is laborious and complicated, and, 
from a great part of his experiments, little information can be 
derived. He found that water dissolved a small portion of 
James' powder, and that what was dissolved consisted of lime 
in combination with phosphoric acid, and a small portion of 
metallic oxide. The remainder of the powder he subjected 
to the action of acids and other re-agents, and was led to con- 
clude that it consisted of fort)^-three per cent, of phosphate 
of lime, and fifty-seven of a calx, i. e. oxide of antimony, 
which he believed were united together as a triple compound. 
He detected a trace of iron in James' powder, occurring as 
an accidental impurity; and Mr. Phillips notices the same cir- 
cumstance in his experiments on pulvis antimonialis. This, 
most likely, is in both cases derived from the apparatus em- 
ployed in the manufacture, and probably accounts for the fact, 
that even with colorless muriatic acid the James' powder 
gives a solution of a slightly yellowish tint. 
The paper of Mr. Chenevix [Phil. Trans. 1801,) is writ- 
ten chiefly with the intention of suggesting the propriety of 
preparing the powder by precipitation, by which means the 
uncertainty always attending the action of furnace heat 
might be avoided. He proposes to dissolve together in mu- 
riatic acid the protoxide of antimony and phosphate of lime, 
and to precipitate them by ammonia. This might certainly 
give us a useful preparation of the protoxide of antimony, but 
it would be widely different from James' powder, which con- 
sists of the peroxide, a substance of a totally dissimilar nature. 
VOL. IV. — no. n, 90 
