iM Of the Arsenic 



In order, however, to difcover the genuine pro- 

 per nature of this fmutting fubftance, I have, as" 

 fuppofing it to be a fat, inflammable earth, di- 

 gefted the white cryftalline arfenic, after rubbing it 

 fine, along with inflammable matters, as exprefTed 

 oil of almonds, and by fublimation procured a 

 quite dark-grey fublimate. Again, treating it in 

 the fame manner with iron- filings, by this means, 

 along with fome white cryftalline flowers, I have 

 obtained a dark-grey arfenic -, fo that the black 

 matter arifing along with the arfenic from arfenical 

 ■pyrites, is to be afcribed to an iron earth ; efpeci- 

 ally as it is otherwife evident, that no arfenical py- 

 rites is without it. 



I alfo found quickfilver alone capable of with- 

 holding this blacknefs, and alfo the yellownefs of 

 yellow arfenic, and of raifing the arfenic alone in 

 beautiful white cryftals ; a circumftance, fure, 

 worth no fmall degree of attention. It is pretty 

 heavy, nay, to a degree of making it fufpec^ed of 

 containing fomething metallic, even mould it be 

 unknown in its native form ; it is partly tranfpa- 

 rent as glafs, partly of a milky colour ; and what 

 was tranfparent, in time, lofes that quality, be- 

 coming externally, alfo, of a milky colour, parti- 

 cularly by means of the free accefs of the moid 

 air ; neverthelefs, it continues fparkling or min- 

 ing, and, againft the light, if newly broke, with 

 its fhivers, appears fmooth, and internally tranf- 

 parent; but, by degrees, it lofes all its tranfpa- 

 rency, and that iboner or later, according to the 

 fize of the pieces or fhivers, and the nature of the* 

 place they are in ; 'till at laft, ftill retaining its 

 fplendor, and without falling, or turning to a 

 powder, it becomes throughout of as milky a co- 

 lour 



