in the Pyrites. iSi 



In the arfenk-butSy which are chambers where 

 the arfenic is refined and purified, arfenic again 

 exhibits the appearance of a fine meal, or of 

 a crystalline body ; both ways, fometimes of a 

 white, fometimes of a yellow, fometimes of an 

 orange call : yet it ought not to be diftinguifhed 

 fo much by being a meal, or powder, and a fluxed 

 body, as by the variety of its colours; for the 

 powder is convertible to a cryflalline body, and 

 this laft may be reduced again by a heedful fubli- 

 mation, to a meal, and the meal again converted 

 to fly-Hone. Now, as the meal, either yellow or 

 white, turns moflly, nay, wholly to a cryflalline 

 body, we mall here the rather treat of the cryflal- 

 line form of arfenic, and as the yellow and orange 

 colours remarkably differ from the white, we muft 

 fay fomething to three forts of arfenics^ namely, 

 white, yellow, and red. 



Arsenicum cryfiallinum album, white cryflalline 

 arfenic, is a white, confiderably ponderous, fluxed, 

 glafly, tranfparent body, brought to that form by 

 means of por-afh and fublimation. The pot-afh 

 principally ferves for purifying, or for, at leafl, 

 retaining and confuming that fuliginous matter 

 lodged in the arfenic, and which makes it of a 

 greyifh caft; be luch matter only from an inflam- 

 mable earth, or, as it alio fometimes happens, from 

 fulphur itfelf. Whether it have any other effect 

 thereon, muft be learned from a careful examina- 

 tion, made exprefsly, both of this cryflalline ar- 

 fenic, and the crude arfenic -meal, and from a can- 

 did comparifon of the feveral proofs made, the fe- 

 parate confideration of which would here carry me 

 too far. 



N 3 In 



