170 Of the Arsenic 



degree of brittlenefs, and hence evidently appears 

 to want a principal characteridic of a genuine me- 

 tal •, nay, it is not, like zink, femi-malleable, but 

 quite brittle, like a bifmuth and regulus. 



In the air it becomes black all over externally, 

 whereas frefti . out of the retort, at lead for the 

 mod part, it is of a mining bright, like a mir- 

 ror ; and each frefh fragment or fhiver of it, broken 

 in the morning, has a black fkin upon it by night ; 

 fo confiderable is the ingrefs of the air into this, 

 that the like is not known in any other metalli- 

 form body, either bifmuth, or regulus. It is further 

 remarkable, that fome genuine, though imperfect 

 metals, as iron, copper, and lead, are more ob- 

 noxious to the action of the air than thefe lad, as 

 appears by the ruft, verdigreafe, and cerufe, they 

 feverally yield. In a word, arfenic, in its genuine 

 form, is a femi- metal, a middle metal, and a fu- 

 gitive metal. 



But arfenic is, in this femi- metallic form, lead 

 of all known, appearing not fo often therein, as jn 

 other forms •, and thus I am obliged to defcribe it 

 in every difguife it wears, both as exhibited by na- 

 ture, and the various procefles of art. 



Arfenic appears either in a reguline, a powdery, 

 or a glafly form •, or as mineralifed, or reduced to 

 an ore-date, a Jlaggey and Honey body. In a re- 

 guline form, it is found either fublimed, and forced 

 off, or as if cad in a cone, like glafs of anti- 

 mony. 



Of the fublimed I have fpoken above, and mud 

 dill add ; fird, that thus it is extreamly flakey, 

 light, and porous, and unlike any other fmelted 



reguline 



