2QZ Of the Arsenic 



nature and encheirefis of arfenic* may in this fame 

 native fandarach, hit upon fomething to his pur- 

 pofe. The means of feparating the arfenic from its 

 adhering fulphur, and thus exhibiting it pure, is to 

 add fomething, to which the fulphur more readily 

 fattens ; whereby it will let go the arfenic. This 

 is the foundation of all feparatioraL and what gives 

 a hint for finding out other means lb the fame end, 

 that would otherwife remain unknqwn. 



(4.) Arfenic is found alrnofHh all, or at lead 

 mod ores; fometimes only incidentally, fometimes 

 eflentially : in fuch manner, that befides its little or 

 no other fugitive fubftance, capable of reducing me- 

 tals to their ore- (late, which fulphur and arfenic 

 alone effect, can be fhewn from ores ; incidentally 

 it lodges in almofb all fulphur -pyrites* as may cer- 

 tainly be concluded from the del ujphuration of the 

 pureft fort ; from the never-failing grey colour of 

 crude fulphur; and from the fandarach, tho' fmall 

 in quantity, procured from fining fuch crude ful- 

 phur-, though fome forts of pyrites, particularly 

 the round, yet that not always, ftand excepted. 

 The copper-pyrites and copper-ores contain fome- 

 what more of it, and the richer in it, the richer 

 they prove in copper, and the poorer, the lefs cop- 

 per they afford : and by my experiments, none is 

 procurable from them when they are purely mar- 

 tial ; and in a fort of copper-ores, looking almoft 

 like a white pyrites, in the volatile part the arfenic 

 is the principal •, whence alio the white colour 

 arifes •, whereas otherwife in copper-pyrites and ores, 

 the fulphur generally predominates. 



In the lead-glitter, the lead has left but very little 

 room for it, being almoft all of it, enveloped in 

 pure fulphur. On the contrary, arfenic lodges ef- 



fentially 



