go PHILOSOPHICAL TRANSACTIONS, [aNNO 17Q1. 



of the piilvis antimonialis were a little specifically heavier than those of James's 

 powder. The specific gravity of both powders was increased by exposing them 

 to such a degree of fire as brought them into almost a semi-vitrified state ; and, 

 on the contrary, the specific gravity of the puU'is antimonialis was less than it is 

 in its usual state, when made in such a degree of fire that the mixture preserves 

 the powdery form. 



The experiments with watef on the pulvis antimonialis produced the same kind 

 of appearances, but more slightly than those with James's powder ; for the hot 

 solution of the former grew less milky on cooling than that of the latter, and 

 on evaporation to dryness less sediment was found of the solution of pulvis an- 

 timonialis than after that of James's powder. The experiments with acetous 

 acid on the pulvis antimonialis shewed, that this menstruum dissolved sometimes 

 a greater, and sometimes a smaller proportion of it than of James's powder ; 

 and the dissolved matter was found to be antimonial calx, phosphorated lime, 

 and calx of iron, and no other substance. It has been already said, that the 

 proportion of soluble matter in nitrous acid was the same, or nearly so, of the 

 pulvis antimonialis as that of James's powder ; and this dissolved matter was 

 phosphoric acid, calcareous earth, with a little antimonial calx, and a minute 

 portion of calx of iron, as exactly as could be expected from the nature of the 

 substances and the experiments, in the same proportion as those in James's 

 powder. The algaroth powder, obtained by means of solution of the pulvis an- 

 timonialis in marine acid, was in the same proportion as nearly as could reasonably 

 be expected from the nature of the experiments as that obtained from James's 

 powder. And the part that resisted solution in this menstruum was partially re- 

 ducible to a metallic form, and had otherwise the same properties, as far as dis- 

 covered, as the insoluble part of James's powder. 



Having now formed a powder possessed of properties similar in kind to every 

 one of those ascertained in James's powder, with scarcely any difference in the 

 degree of them, if it be thought that among those properties are those which are 

 essential and peculiar ones of James's powder, the conclusion that these 2 are the 

 same kind of things must be admitted to be just. The nature of one of the ingre- 

 dients of James's powder, viz. the irreducible part of the insoluble matter, is not 

 fully elucidated by the synthetic experiments ; but in so far as they show that this 

 part equally exists in the powder formed by calcining together antimony and 

 bone, which is concluded to be James's powder, tlie objection against the con- 

 clusion with respect to the identity of the 2 substances, on the ground of this 

 inconsiderable part of James's powder not being well understood, must be of 

 little weight. 



Several reasons, more interesting to myself than to the Society, induced me 

 to authenticate by additional testimonies those analytic experiments, which may 



