1819.] Berzelius on a new Mineral Body, be. 257 



Article IV. 



Researches on a new Mineral Body found in the Sulphur extracted 

 from Pyrites at Fahlun. By J. Berzelius. 



(Continued from p. 106.) 



6. Seleniuret of Copper. — If we precipitate sulphate of copper 

 by seleniuretted hydrogen gas, we obtain a seleniuret of copper 

 in black flocks, which, when dry, become of a dark-grey colour, 

 and may be polished by a hematite. Exposed to a red heat in 

 a distilling apparatus, this seleniuret gives out one-half of its 

 selenium, and leaves a melted button of protoseleniuret of copper. 

 This last seleniuret is easily formed with the evolution of heat 

 when copper and selenium are heated together. The compound 

 becomes liquid long before it is heated to redness, and gives a 

 steel-coloured button with a compact fracture, very like grey 

 sulphuret of copper. When exposed to the naked fire, it first 

 loses a certain epiantity of selenium, after which it undergoes no 

 further alteration, and after being long roasted, it still yields a 

 mass more fusible than copper, which breaks under the blow of 

 a hammer, and exhibits a fracture of a grey colour. 



7. Seleniuret of Lead. — Selenium and lead unite with the 

 production of heat. The lead swells, and gives a porous mass of 

 a grey colour, which does not melt at a red heat, which easily 

 receives impressions, admits of being polished, and then assumes 

 a silver-white colour. When heated, seleniuret of lead gives out 

 first a little selenium, and then evaporates in a white smoke. 

 The r - esidue gives at a high temperature marks of a commencing 

 fusion. Seleniuret of lead exposed to the flame of a blow-pipe 

 loses a part of its selenium, becomes oxidized, and produces a 

 subseleniate of lead, which afterwards suddenly penetrates the 

 charcoal, is decomposed, and leaves upon the surface of the coal 

 a white pellicle of seleniuret of lead reduced. Lead at a high 

 temperature is capable of uniting with a little seleniuret of lead. 

 By this union, it becomes whiter, and less fusible. 



8. Seleniuret of. Silver. — Silver is blackened by the fumes of 

 selenium. If we heat the metal with an excess of selenium, 

 heat is disengaged, and a very fusible mass is produced, from 

 which the excess of selenium may be separated by distillation. 

 The compound has a grey colour, and while it remains liquid, its 

 surface is brilliant, and polished like a mirror. This seleniuret 

 is fusible at a temperature greatly below that of a red heat. 

 When cold, it is grey, somewhat ductile, and may be flattened a 

 little before it breaks. When heated before the blow-pipe, it 

 loses a portion of its selenium, and with it a good deal of its 

 fusibility. In a strong fire, kept up for some time, it continues 

 liquid ; but very little of the selenium is disengaged. The sele- 



Vol. XIV. N" IV R 



