of Copper and of Iron. 3*^7 



degree of oxidation,) yielded up its entire (hare of oxygen, to • 

 favour the combinations which take place in a new order, 

 the only one which can exill among the fubflances now pre- 

 fent. ft is, therefore, to the difpofing affinity*, caufed by 

 the prefenc^; of the phofphoric acid, which feeks to combine 

 with black oxide of copper, that the reduttion of 42 per 

 cent, of this ore is entirely to be attributed. All the acids 

 above mentioned are capable of producing the fame change, 

 but in a manner, perhaps, not quite fo diftinft or fatisfaftory. 

 From the foregoing experiments it appears, that copper 

 exids m this ore in a ftatc hitherto unknown in nature ; and 

 that it contains much lefs oxvgen than has ever been fuf- 

 pe6ted in any oxide of copper; tor, from the quantity which 

 was precipitated in the metallic ftate by iron, it appears to be 

 combined in the proportion of about 1 1,5 per cent. To con- 

 firm this idea, and afceriain, as nearly as I could, the precife 

 quantity, I diflolved 100 parts in nitric acid; then boiled 

 with p()iafli, and filtered. One hundred and eleven remained 

 iipon the filter, which, as they had combined with a new 

 portion of oxygen from the nitric acid, were in the ftate of 

 black oxide, and correfpond exaftly to 88,75 5 ^o that I be- 

 lieve I ftiall be within one per cent.' of the truth, in aflerling 

 the proportions to be. 



Copper - - 88,5 

 i:^ Oxygen - - 11,5 



7 00,0 

 When, into a folution of muriate of fuboxide of copper, 

 liquid potafti or foda is poured, a bright yellow precipilate, 

 not unlike the precipitate of platina, takes place. T his pre- 

 cipitate difiers only in colour from the original ore; for it ii? 

 foluble in muriatic acid, and atfords the lame folution and 

 precipitation by water, and the fame appearance with alco- 

 hol. It is likewife foluble in nitric acid, but with difcngage- 

 ment of nitrous gas, and gives the fame appearances with 

 the other acids above enun^erated. The diiVerence of colour 

 feems to arife merely from the tenuity of its molecules, com- 

 pared to the mechanical pulverization of the natural oxide. 

 When al(jne and dry, it is much more permanent in its na- 

 ture than when combined with muriatic acid; but any part 



• A« tliL- uxm p^'t dt fpijing affi>iit\ lias been objcfttcd to, I have ult-il the 

 rerm it>lp')/hiy,, whitti. I tnift, will not be thought improper. When in 

 two bodies which, while together, rcni<iiii in their oii^iniil It-itc, th<rvi)iii- 

 libriuin of their printij Ics come* to he broken by tlic prel'entc ot a tliiril, 

 wc cannot but hIIow that it is this thin! which has Jirjioffd them to the 

 niptur. i.f that e<|iiili')r'um ; and, mort certainly, be the fii£t CKilaiiied as 

 it may, whatever dilpoles may be ct1Ii.iI difpufitig. 



U a of 



