CHEMISTRY OF COPPER SULPHIDE 271 



and it is known that solutions of cupric salts are reduced to cuprous 

 salts by boiling with sulphurous acid. * Moreover, sodium thiosulphate 

 added to hot solutions of copper salts gives a black precipitate of cuprous 

 sulphide, t It therefore becomes at once apparent that the precipitat- 

 ing agent in these veins can not have been a soluble sulphide unless 

 there were at the same time a reducing agent strong enough to reduce 

 the cupric sulphate to cuprous sulphate and precipitate cuprous sulphide, 

 and not strong enough to reduce it to native copper. 



Literature of Copper Glance 



The mineral chalcocite has been formed, both artificially and natu- 

 rally, in recent times, and is referred to by numerous writers as follows : | 



Daubree § found chalcocite crystals accidentally developed on coins 

 and copper instruments which had lain for a long time in damp ground, 

 as at Bourbonnes-les-Bains, Plombieres, etcetera. 



De Gouvenain || found crystals of copper glance on fragments of 

 copper which had been for some time in the warm spring of Bourbon- 

 I'Archambault. 



Rammelsberg^ discovered two small cubical crystals in furnace pro- 

 duct from Mansfeld containing iron, nickel, cobalt, zinc, and manganese 

 ison)or})hous with the copper. 



Scheerer** found small rhombic crystals, supposed to be chalcocite, in 

 a reverberatory furnace at Freiberg. 



Mitscherlich ff obtained octahedral chalcocite artificially by melting a 

 proper mixture of copper and sulphur. 



Durocher JJ reproduced the rhombic variety by heating in a red-hot 

 tube vapor of copper chloride and sulphuretted hydrogen. 



Becquerel §§ obtained copper glance in hexagonal plates by the same 

 method which he employed in the formation of galenite. 



Senarmont |||| obtained only an amorphous precipitate by warming to 

 200° in a sealed tube a mixture of copper sulphate, bicarbonate of soda, 

 and potassium sulphide. 



*Kohner: Chem. Centralblatt, 1886, 813. 



t Vortmann : Monatshefte fiir Chemie, 1889, 9, 165. 



I Fouqu6 and Levy : Synthase des Min6raux des Roches, p. 294; M. L. Bourgeois : Reproduction 

 artificielle des mineraux, 1884, p. 38; Meunier: M6thodes de Synthese en Min6ralogie, 1891, pp. 

 69, 75. 



g Daubr6e : Compt. rend., vol. Ixxx, 1875, 461. 



II De Gouvenain : Compt. rend., vol. Ixxx, 1875, 1297. 

 f Rammelsberg : Metalliirgie, p. 224. 

 **Scheerer : Hiitten-Erzeugnisse, p. 366. 



tt Mitscherlich : Pogg. Ann., xxviii, 1831, 157. 

 It Durocher : Compt. rend., xxxii, 1851, 825. 

 §§ Becquerel : Compt. rend., xxxii, 1852, 38. 

 nil S6narmont: Ann. ph. eh., xxxii, 1851, 129. 



