VOL. LXXXl.j PHILOSOPHICAL TRANSACTIONS. QQ 



fumes disappeared ; after calcining J- an hour longer in a heat that kept the 

 bottom of the dish red-hot, the mixture was of a reddish brown or copper 

 colour, and after cooling weighed 2520 grs. Supposing therefore the whole de- 

 ficiency of weight in this experiment to be from the sulphur carried off; and 

 supposing the quantity of air combined with the metal to be the same as in 

 Exper. 2, the loss of weight, viz. 32 per cent, is more than would have been 

 expected ; but as in experiments of this nature it is not perhaps possible to re- 

 peat them under precisely the same circumstances, the difference of 2-i- per cent, 

 deficiency more than would have been calculated, may more reasonably be as- 

 cribed to the sublimation of antimony than to other causes. By exposure to 70° 

 of fire in a close crucible, this calcined mixture changed to a pale straw-coloured 

 powder, and the sides of the vessel were glazed yellow. The change of colour 

 was the same in an open vessel in 6o° of fire. Though it is probable, from this 

 experiment, that there is an affinity between antimonial calx and vitriolic selenite, 

 it is plain that the compound is very different from James's powder. The next 

 experiment with chalk and antimony, which Dr. Blagden suggested, would lead 

 to several conclusions, but I shall only take notice of the composition produced. 

 Exper. 11. 1200 grs. of antimony were mixed with 800 grs. of well washed, 

 dried, and pulverized chalk, and calcined as in making Lile's powder. In less 

 than an hour the smell of sulphur disappeared ; after which the mixture was cal- 

 cined 4- an hour longer. It afforded a lighter clay-coloured powder than the cal- 

 cination of antimony with bone-ashes ; and weighed 1 800 grs. By exposure to 

 lOO" of fire this powder changed to a dirty white colour. On examination, in- 

 stead of aerated lime or chalk, there was found vitriolic selenite, part of which 

 was probably combined with the antimonial calx ; for, by means of boiling water 

 repeatedly applied till the lixivium did not become turbid with muriated barytes 

 nor with acid of sugar, there could only be obtained 12 per cent, of vitriolic 

 selenite, mixed with a little antimonial calx ; but by means of nitrous acid there 

 was separated 43 per cent, of this selenite, with scarcely any antimonial calx 

 in it. The residuum, after this solution in nitrous acid, was calx of antimony 

 with a little vitriolic selenite seemingly vitrified. Accordingly the composition 

 may be stated to consist of 1000 parts of antimonial calx and QoO parts of 

 vitriolic selenite which is inferred from the quantity of selenite dissolved by the 

 nitrous acid, and estimated to remain united to the calx ; and from the following 

 calculation of the proportion of these 1 ingredients formed in the experiment, 



Antim. Sulph. Air. 

 12C0 — 3'JO + 100 — 1000 antimonial cak. 



Calcar. Aerial Vitriolic 



eartli. acid. acid. 

 800 — 300 + 450 - 950 vitriolic selenite. 

 Sum 1950 

 Loss by sublimation and waste 150 



Difference 1 800 



o 2 



