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XXXVIII. Analyfis of the Arfentates of Copper and of troft^ 

 Bj RicHArxD Chet*evix, Efq. F.R.S. MiR.LA. 



N< 



[Continued from p. 147.] 



O, VII. Yellow hcmathtc copper ore *. (See page 4.) 

 One hundred parts of this ore, boiled with dihite nitrie 

 acid, left a yellowifli white refiduum, which weighed 17, 

 Thefc 17, expofed to a degree of heat fufficient to volatilize 

 the fulphur, left 5, which were filica. The liquor from which 

 this refiduum had been feparated by filtration, upon being 

 tried for all the different metals, and particularly for arfenic, 

 afforded no traces of any thing but copper and iron. A co- 

 pious precipitate took place by the afi'ufion of ammonia ; the 

 copper was redifTolved by adding an excels ; and then obtained 

 by volatilizing that alkali, and boiling with potafli, after the 

 filter had feparated the iron already precipitated. The contents 

 are, 



Sulphur - - - - 15 



Silica - _ _ _ _ ^ 



Copper, which I believe to be in the metallic ftate 30 

 Oxide of iron . _ - _ ^ ^ 



100 



Tn this ore, I believe, for the following reafons, that the 

 metals are in the ftate I have marked. Firft, the propor- 

 tions in the ore announce it ; for I always had an cxcefs of 

 weight in the total refult, if I did not deduft fuch a propor- 

 tion of oxygen as might be contained in 30 parts of copper. 



Secondly, there is a confiderable difengagcment of nitrous 

 gas. 



Thirdly, the ore does not attract the loadftone. 



And, fourthly, the greater part of the iron (but none of 

 the copper) is diffolved in muriatic acid, forming a green 

 muriate of iron, without difengagcment of hydrogen gas. 



No. VIII. Gray vitreous copper ore. (See page 6.) There 

 are many inte-mediate ftates between this ore and the yellow 

 hematilic copper ore; but they are not fair objefts of che- 

 mical analyfis, being merely mixtures of both kinds, in dif- 

 ferent proportions. The mineralogift, indeed, ina\' dwell 

 upon them, as interefting in ftudying the produfts of nature, 

 but they are unfatisfaftory fubjedls for the chemift. 



'"• This ami rlie following f No. VIII.) being the matrices upon whih 

 the ai feniatcs of copper and of iron are generally found, I tliought it right 

 to give an analyfis of thtm alio. 



Gray 



