ON METALLIC SULPHURETS- 149 



"^ame way. I separated by calcination 0*34 of a gr. of sul- 

 •phur. The gangue weighed 0*48 of a gr. The sulphate of 

 barytes obtained weighed 8*88 gr., corresponding to 1*24 gr. 

 of sulphur. The whole of the sulphur therefore wasl*58 gr. 

 The brown oxide of copper weighed 1*73 gr.; the red 

 *xide of iron, 2'l6 gr. 



Result, 



Sulphur 31-5 Componeat 



Copper 28 parts. 



Metallic iron 2g 



■Gangue 9 



97'5 



Mean proportions. 



^ -, ■, Mean of the 



bulpnur > • • • 31 "5 two analyses. 



Copper 27*5 



Metallic iron 29-5 



Gangue 9 



97-5 

 Iliave reason to think, that the proportions of sulphur are Sulphur not 

 1 T 1 11 1 11 1 1 - completely 



Tathertoo small, because all the methods employed never give ascertained, 



the whole of this combustible. 



When metallic sulphurets are treated with nitric acid di- and generally 

 luted in water, the sulphur remains mixed with the metals, than the truth, 

 which become oxided during the evaporation. All the oxi- 

 gen add-ed diminishes the quantity of the sulphur. By em- 

 ploying nitromuriatic acid and boiling, this inconveBience is 

 avoided; but sulphuric acid may be carried of in vapour. 

 Whatever method we adopt, the quantity of sulphur ob- 

 tained may always be considered as below what really exists. 



Notwithstanding the errours unavoidable in analyses, it is Proportions of 

 «asy to perceive, that the relative quantities of sulphur, cop- per^ and iroa" 

 per, and iron, are nearly the same in the two specimens of nearly uni- 

 <;opper pyrites. Setting aside the gangue, and reducing the 

 proportions to hundredth parts of pure ore, we find 



Sulphur. Copper. Iron. 



In the copper pyrites of Sainbel 37 30.2 32*3 



In that of Baigorry 35 30*5 33 



Mr. Proust has shown, that the copper pyrites contains A mixture of 

 sulphuret of copper completely formed, and he considers pii^urels*.^ 

 Ihis mineral as a mixture of the two sulphurets of copper 



and 



