OO Oil a native Arseniuie of Lead, 



copious precipitates of a white heavy matter. If the fluid 

 be poured off* from this subsided matter, and it be freed 

 fn^m the superfluous sulphuric acid, by the means of nitrate 

 of barytes, it will yield, on the affusion of liquid nitrate of 

 lead, an abundant white precipitate, which, urged by the 

 flame of the blow-pipe on a support oF charcoal, resolves 

 itself into reduced lead and arsenical vapours. 



These preliminary experiments led me to the probable 

 conclusion, that this fossil. chiefly consisted of oxide of lead, 

 ilrsenic acid, and a small quantity of the muriatic acid. 



IV. Analysis, 



A, 



1. Fifty grains, carefully selected from crystals of a pale 

 Isabella-colour, were reduced to a fine powder, and exposed 

 to a low red heat for about an hour. Their weight was di- 

 minished by 0*15 of a grain. 



2. The yellowish powder was now transferred to a vessel 

 of pure silver, and mixed with a lixivium containing fifty 

 grains of potash, prepared by the means of alcohol ; a quan- 

 tity, which 1 had previously ascertained to be sufficient to 

 effect a complete decomposition of this mineral. The ley 

 was gradually evaporated to dryness in a sand-bath. The 

 soluble part was extracted by distilled water, and poured off 

 from a yellowish white matter, which was sufficiently edul- 

 corated (a). 



3. Liquid nitrate of ammonia was now dropped into the 

 alkaline fluid, as long as it produced any cloudiness : the 

 clear fluid was now decanted from a small quantity of white 

 matter, which had subsided, and rendered acid by nitric 

 acid; ammonia, added to excess, produced a slight turbid- 

 ness. These precipitates, after sufficient edulcoration, were 

 added to the yellowish white residuum (a). 



4. The liquid was now rendered slightly acid by nitric 

 acid, and a solution of nitrate* of lead in distilled water 

 was dropped into it, as long as it separated any precipitate. 

 The clear fluid was poured off, and evaporated nearly to 

 dryness, and a small quantity of white matter, thus ob- 

 tained, was added to the former precipitate, which dried, 



• If the colourless liquid oxy-nttrate of lead be .dropped into a dilute so- 

 lution of arsenic acid, or of arseniate of potash acidulated by nitric acid, no 

 immediate precipitation of an arseniate of lead is produced; but crystalline 

 grains are, after a time, gradually deposited at the bottom of the vessel. But 

 liquid nitrate of lead causes an immediate and abundant precipitate from 

 these same dilute solutions. These two combinations therefore must be 

 ♦iilferent. 



and, 



