464 PHILOSOPHICAL TRANSACTIONS. [ANNO 1799. 



More or less of these oily particles were discovered in every successive operation; 

 and the oily matter, adhering to the inside of the glass, increased considerably. 



Exper. 5 1 . When the fluid was distilled, the receiver was changed, and the fire 

 increased. A considerable quantity of sublimate was obtained, pretty white in 

 colour, as was also the surface of the mass of salt at the bottom of the retort; but 

 lower down it was almost of a light ash-grey. After the sublimate ceased to arise, 

 I diminished the fire. 



Exper. 52. On the mass of the former experiment, I poured the fluid, obtained 

 by exper. 49, and continued a gentle digestion. I very soon perceived something 

 rising towards the surface, and swimming on it: after some hours, it appeared to 

 be a thick wrinkled skin, like fat, or a skin of mould, increasing in size, till it 

 covered the whole surface. White spots of sublimate appeared on it, but it did 

 not sink. It assumed gradually a fine lemon colour, and some yellow matter, 

 though not in large quantity, ascended the sides of the retort. The fluid having 

 been gently distilled, and the receiver changed, I placed the retort in an open fire; 

 on which, more sublimate soon appeared; but, not long after, it all vanished, and 

 the retort lost its transparency. The mass contained in it began to rise, first 

 gently, and then violently, especially in the centre, in large frothy bubbles. The 

 distillation was finished, after obtaining 1 dr. of fluid, and when the frothy bubbling 

 had ceased. The retort being broken, that part where the bubbling had been 

 strongest, was found to be black ; the upper surface being covered with a thin 

 greyish matter, under which a solid, compact, and almost vitrified substance ap- 

 peared. On this I poured water, and dissolved it in the usual manner; filtered it, 

 let it evaporate, and treated it as described above, exper. 22 — 30. 



Exper. 53. I obtained a white salt, a, and some coal, b, which deflagrated 

 briskly with nitre, in nearly the same proportions as throughout the series of expe- 

 riments described from exper. 20 to 33, which I will not repeat, on account of 

 the little variety observed in them ; one of them however deserves to be distin- 

 guished from the rest. — Exper. 54. I put 6 gr. of the coal, b, of exper. 53, in 

 3 dr. of common muriatic acid, and digested them for 2 days, till the acid had 

 gradually evaporated. I then added 1 dr. of the same acid, with 1 scruple of nitric 

 acid, and when they had evaporated, boiled the residuum full half an hour in 

 distilled water. By this process, I obtained a red solution ; and, having saturated 

 it with mild alkali, a sort of skin rose to the surface, with some small pieces of a 

 fat slippery substance, a. A considerable quantity of loose earth, b, was also 

 precipitated, of a light brown colour. — Exper. 55. On throwing the floating pieces* 

 a, of exper. 54, into a solntion of caustic alkali, they dissolved; the solution had 

 a reddish-brown colour. — Exper. 56. With the same solution of caustic alkali, I 

 covered the light brown earth of exper. 54. As the solution changed its colour to 

 a reddish brown, the earth gradually became perfectly white. — Exper. 57. To ob- 

 serve the affinity of other acids to the sedativesalt, I poured6 dr. ofnitrous acid on2dr. 

 of the salt, with 10 dr. of the oxygenated fore-mentioned muriatic acid; digested the 



