VOL. LXXXIX.] PHILOSOPHICAL TRANSACTIONS. 46l 



down, and in many places of a yellow colour; it extended even into the neck of 

 the retort, and almost covered the interior aperture of the tube. — Exper. 17. The 

 13th distillation produced the same phenomena. On the lowermost surface of the 

 mass of salt, many light-brown spots appeared, as soon as the fluid was so much 

 evaporated that no more of it could be seen on the salt. — From all these circum- 

 stances, I now believed the mass of salt, by a digestion of 22 days, and 7 distilla- 

 tions, from exper. 11 to 17, that is, by a digestion of 54 days, and 13 distilla- 

 tions, in the whole, to be so far decomposed, as to admit of a separation of some 

 of its constituent parts. I therefore supposed I might leave off applying only 

 digestive warmth, and proceed to a greater degree of heat. 



Exper. 18. Having poured out the fluid obtained by exper. 17, and replaced 

 the phial, I increased the degree of heat. By this the retort became quite obscured, 

 first by fumes, and afterwards by a quantity of white sublimate, attaching itself to 

 all its sides, which however had not the appearance of common sedative salt. As 

 I increased the heat, the sublimate became dark in colour; afterwards became black 

 and frothy: and at length ran down the sides of the retort, in different places, like 

 thick oil of hartshorn, the retort being almost wholly blackened by it. — Exper. lg. 

 While the retort was still warm, I poured into it the fluid obtained by exper. 17, 

 having first warmed it a little; when, almost in the same instant, a very agreeable 

 phenomenon took place. Crystals, perfectly white, shot forth suddenly, and all 

 at once, from every part of the black mass, covering the sides of the retort. The 

 distillation being continued, these crystals were at length dissolved, and entirely re- 

 moved. The supernatant fluid was, as usual, almost colourless. When the mass 

 of salt appeared dry, the fire was increased, as in exper. 18, and the same appear- 

 ances as above related took place: first, the sublimate appeared white, then black, 

 frothy, and flowing down the sides. — Exper. 20. I proceeded, as in exper. 19, to 

 pour back the distilled fluid. Instantly a number of the whitest crystals shot forth 



from the black ground, forming small groups; but the retort was cracked. 



Exper. 21.1 therefore took all the vessels asunder, and shook the retort well, till 

 whatever hung on its sides was dissolved; then distilled the fluid in another retort, 

 till the mass of salt appeared quite dry. I now put the retort into a crucible, sur- 

 rounded it with sand, fitted another receiver to it, and placed the crucible in an 

 open fire. First, some sublimate was produced, towards the neck of the retort, 

 but which vanished as the heat increased, and then a small portion of fluid, hardly 

 more than a dram, or a dram and a half, which appeared to smell a little of the 

 sebacic acid. At the bottom of the retort was a blackish mass, a, and likewise 

 some sublimate, b, which, by its varied appearance, seemed to be of a two-fold 

 nature. 



Exper. 22. The residuum taken out of the broken retort had a spongy appear- 

 ance, and swam on water; it had a blackish colour, and weighed 3 dr. 10 gr. Being 

 exposed to the air, the blackish colour became lighter, and inclining to grey. When 



