2p6 TfoVlTRlOL 



This collective air Jays hold on and attacks the 

 pyrites, and without it we are never to expect any 

 vitriol, not even the fpontaneous vitriolcfcence of 

 pyrites. For, tho' I have had no opportunity of 

 making any experiments with the air-pump, yet I 

 have obferved, that pyrites, when kept in a very 

 clofe glafs, efpecially in a dry and rare air, vitrio- 

 li/es with more difficulty than without the glafs : 

 and from this gradual difference it feems, that were 

 it poffible entirely to exclude the air, a pyrites 

 would with the more difficulty, or not at all, be- 

 come vitriolic. In fhort, the air is entirely necef- 

 fary for the purpofe, and that according to all and 

 every property thereof, not in its feparate but col- 

 lective nature. For that the water alone is inef- 

 ficient, appears from the pyrites not giving in the 

 leaft, tho' lying, nay boiled in water never lo long •, 

 as little effect has the vitriol-acid alone, feeing the 

 pyrites remains whole, entire, and unchanged in 

 the ftrongeft vitriol-acid \ nor are both thefe toge- 

 ther fufficient; the affair depending not io much 

 on the matter of the air, as on its motion, its foft 

 and gentle attack, its wavy ambiency and infinua- 

 ting impreflion, in order to theaccomplifhing thefe 

 ceil ructions, and procuring new productions. 



It has been already mentioned of white pyrites, 

 that it yields no vitriol, tho' its arfenic, of which it 

 principally confifts, yield in fome meafure to the 

 air, as I have mentioned above of the fly -ft one : it 

 istheyellowifh, or un\verfa\fulpbur -pyrites and the 

 copper-pyrites, or the yellow copper-ore, that are 

 properly fubject to the action of the air •, tho' for 

 their improvement and exaltation, yielding (lowly, 

 and with fome degree of rtfiftance ; and with this 



remark- 



