METALLIC &ULPHTJRETS, 



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The grey ore of copper of La Cren, in tlie kingdom of 

 Valentia, is of this kind : it is compofed of four fulphurets, 

 that of copper, of iron, of antimony, and of mercury. De- 

 pofited in manes in the calcareous breccias formed by the re- 

 mains of mountains which no longer exift, it undergoes a de- 

 composition at its furface, which converts three of the ml- 

 phurets into oxides, whilft that of mercury remains entire, 

 and imparts to the decompofed ore a brilliant vermilion hue. 

 At the centre there is always a nucleus compofed of thefe four 

 fulphurets in their entire ftate. The analyfis of this mineral, 

 given by Fernandez, is in the Annates : but I return to the 

 fulphuret of copper, from which I did not intend to digrefs. 



Thofe which I have had opportunity to examine contain Copper pyrites, 



from 14. to 15 per cent, of fulphur, which is eafily extruded like that of iron, 

 r ,, ■ i contains an ex- 



from them by a moderate heat, and what remains in the retort ce f s beyond the 



is always the blue fulphuret, faturated according to an uniform ftate of fulphu- 



proportion. This proportion is 18 per cent, like that of the 



artificial fulphuret. Jf a native fulphuret of copper leaves 86 



of refiduum, we may precipitate its nitric folution by fulphu- 



rated hidrogen ; and the precipitate feparated from the exeefs 



of fulphur re-produces 86 parts of fulphuret of copper. Hence 



we fee, that though the native fulphuret is fubjecl to an exeefs of 



fulphur, it does not on that account differ from the artificial 



fulphuret, when it has been deprived of this exeefs. 



By the action of a red heat, the oxides of copper, mixed Copper fulphu- 

 with fulphur, yield only blue fulphuret. This metal does not e x j gen# 

 afford a fulphurated oxide, either in nature or in the products 

 of art. Its formation is always attended with a confiderable 

 extrication of heat, It is aftonifhing, if it be duly coniidered, 

 that it could ever for one moment have been rmftaken for a 

 combufKon, 



The blue fulphuret diffolves in copper, and forms the black Black copper, 

 coppers, independently of the iron which they may contain. 

 Acids of 10 or 12 degrees feparate it from thefe coppers with- 

 out ^ecompofing it. 



On the Fuming Muriate of Tin, 



Since the year 1777, I have been in the habit of preparing Fuming muriatt 



this muriate with corrofive fublimate and pulverifed tin; and of ^ n P**?*™* 



r ' without amalga- 



though I never thought of publifhing this procefs, it was be- mation. 



caufe I imagined it to be in common ufe in every laboratory. 



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