462 PHILOSOPHICAL TRANSACTIONS. [ANNO 1 7QQ. 



digested in 16 parts of distilled water, in the usual temperature, for 2^ days, it 

 did not all sink to the bottom; and after being digested with heat for 20 hours, it 

 was not entirely dissolved: that part which sank, was of a blackish brown. More 

 water was then added, and it was made to boil for 2 hours ; it was afterwards placed 

 on a paper filter, the weight of which was previously ascertained, and edulcorated 

 with boiling distilled water, till at last a proportion of 26 parts of water to the 

 substance had been used. After all the fluid, a, had passed through, and the 

 filter, with the residuum, had been dried in a heat of 212°, for an hour and a 

 half, the residuum, (3, weighed, exclusive of the filter, lQgr. — Exper. 23. The 

 fluid, a, obtained by exper. 21, was suffered to evaporate gradually, and yielded 

 3 dr. 10 gr. of a white transparent salt. — Exper. 24. This salt, obtained by exper. 

 23, was put into a small retort, and exposed, in a crucible filled with sand, to an 

 open fire. It became of a blackish-brown colour, yielded some sublimate, a, 

 about 5 gr., a small portion of fluid, b, and a blackish-brown residuum, c, which 

 became lighter in colour, on being exposed to the air. — Exper. 25. The fluid, b, 

 of exper. 24, smelled like marine acid, and precipitated nitrate of lead. — Exper. 

 26. The residuum, c, of exper. 24, by the addition of some water, became 

 whiter, and was dissolved ; more water having been added, it was digested with 

 heat, by which the matter was dissolved. The solution being afterwards filtered, 

 I obtained 2 dr. 4 gr. of white salt : the residuum on the filter weighed 4 gr. — 

 Exper. 27. This salt, exper. 26, was again exposed to the fire; when it yielded 

 from 20 to 30 drops of acid liquor, 4 gr. of sublimate, and a residuum which, 

 being dissolved, yielded 1 dr. 33 gr. of salt, and left 24 gr., c, on the filter. 



The same salt, obtained by Exper. 26, being distilled, became of a brownish 

 grey colour; and, besides a few drops of fluid, yielded not quite 2 gr. of sublimate. 

 On treating the residuum with water, it yielded 68 gr. of salt, and there were not 

 quite 2 gr. left on the filter. 



Exper. 28. On treating these 68 grs. of salt in the same manner, they yielded a 

 few drops of fluid, and 2gr. of sublimate: after filtration, there remained 48 gr. 

 of salt, and a residuum of hardly Hgr. — Exper. 29. The same salt, treated in 

 the same manner, yielded a few drops, and a little sublimate; and after filtration, 

 35 gr. of salt, and a residuum of hardly 1 gr. — Exper. 30. On treating these 35 

 grs. of salt in the same way, they yielded, besides a very small quantity of fluid, 

 and of sublimate, 24 gr. of salt, and about \ gr. of residuum. — As I now dis- 

 covered that the quantity of salt was continually decreasing, and some coal sepa- 

 rating from it, I thought it superfluous to endeavour to decompose the above 24 

 gr. any further. 



Exper. 31. The residuum, (3, of Exper. 22, was light, blackish, and like coal. 

 I now poured common concentrated muriatic acid on 3 grs. of it, and digested the 

 mixture for 42 hours, in a considerable degree of heat, but no dissolution was 

 apparent. I then added smoking nitrous acid, and digested it for 24 hours, till it 



