1819.] extracted from Pyrites at Fahlun. 259 



other portion of that acid dissolves with the corrosive sublimate. 

 This phenomenon sometimes took place when selenium was 

 extracted from red sulphur, and embarrassed me at first a good- 

 deal. I could perceive no reason for the reduction of the sele- 

 nium by the addition of muriatic acid, especially after ascertain- 

 ing that no chlorine was formed. I found at last that it was 

 owing to the formation of a little protoseleniate of mercury, 

 which precipitates along with the sulphur not dissolved. 



Seleniuret of mercuiy dissolves rapidly in nitromuriatic acid, 

 even without the assistance of heat. 



10. Seleniuret of Bismuth. — This combination takes place 

 with the evolution of a little heat. It melts at a red heat, and 

 then has a polished surface. When cold, it has the metallic 

 lustre, a silvery colour, and its fracture is crystalline. 



1 1 . Gold and selenium do not combine when heated together ; 

 but I have no doubt that a compound of them may be obtained 

 by precipitating a solution of gold by seleniuretted hydrogen gas. 



12. Seleniuret of Palladium. — Palladium combines readily 

 with selenium, and heat is evolved. The compound is grey, 

 coheres together, but does not melt. Before the blow-pipe 

 selenium is disengaged, and when the heat is strong, the sele- 

 muret melts into a grevish-white metallic button, brittle, and 

 having a crystalline fracture ; it still, therefore, contains selenium. 



13. Se/e?iiuret of Platinum. — Selenium combines very readily 

 with platinum in powder, occasioning the evolution of a strong 

 heat. The compound is a grey powder, not fused. In the fire, 

 the selenium is easily oxidized, and leaves the platinum pure. 

 Platinum crucibles are easily attacked by the seleniates when 

 they are heated to redness in these vessels, or when dry seleniate- 

 of ammonia is evaporated in them. The surface of the metal 

 acquires a brownish-grey colour, and cannot be cleaned ; but 

 the selenium is volatilized if the crucible be heated to redness 

 without being covered. 



14. Seleniuret of Antimony. — These two bodies unite easily 

 and with the production of heat. The compound melts into a. 

 metallic button, having a crystalline, fracture. If it be strongly 

 heated in the air, it becomes covered with a vitreous scoria. 



15. Seleniuret of Antimony with Oxide of Antimony. — These 

 two substances easily unite, and form a yellowish-brown mass, 

 transparent when in thin layers, vitreous, and quite analogous 

 to what is called glass of antimony. 



16. Seleniuret of Tellurium. — The two substances unite with, 

 the production of heat. The compound is very fusible. When 

 heated, it boils and sublimes in the form of a metallic mass, of a 

 deep brown colour. It is easily oxidized, and leaves on the glass 

 transparent colourless drops, which are not volatile, and appear 

 to be seleniate of tellurium. The sublimed mass melts long 

 before it is heated to redness. It is very liquid, without any 

 tenacity, and cannot be drawn into threads like selenium alone. 



x2 



