258 Berzelius on a neio Mineral Body, [Oct. 



niuret thus treated has become more ductile, and may be 

 flattened considerably ; but it breaks at last, and exhibits a 

 foliated fracture. 



When we precipitate a solution of silver by seleniuretted 

 hydrogen gas, we obtain a black powder, which, when dry, 

 assumes a deep grey colour. The seleniuret requires a red heat 

 for fusion, does not yield selenium when distilled, and leaves 

 after cooling; a silvery metallic button. When heated before the 

 blow-pipe, it loses little of its selenium, and exhibits the same 

 phenomena as the seleniuret obtained by the dry wav. These 

 facts seem to prove that selenium is capable of uniting with 

 silver, at least in two proportions ; both of which compounds are 

 permanent at a red heat, and in close vessels. The perseleniuret 

 is much more fusible than the protoseleniuret. It gives out the 

 excess of its selenium when roasted, and leaves the protosele- 

 niuret, which may likewise be produced by seleniuretted 

 hydrogen gas. Silver cannot be deprived of selenium by fusion 

 either with borax or an alkali. Even iron does not separate it, 

 as is the case with sulphur and silver. If we heat seleniuret of 

 silver with iron, they combine, and the mass enters into fusion 

 at a somewhat elevated temperature. This triple compound is 

 brittle, its fracture is granular, and of a deep yellowish-grey 

 colour. If we fuse this mass with borax, it dissolves the iron 

 and selenium, and we obtain a button of pure silver surrounded 

 with a black vitreous matter. 



Seleniuret of silver may be dissolved by boiling nitric acid. 

 The liquid deposits as it cools small crystals ofseleniate of silver. 

 If we pour water into the liquid, the seleniate precipitates in the 

 state of a white powder. 



9 . Seleniuret of Mercury. — Selenium and mercury combine when 

 they are heated together. I have not observed any evolution of 

 light during this combination. If there be an excess of mercury, 

 it may be separated by distillation, and in the retort there 

 remains a coherent white mass like tin. It does not melt ; but 

 at a somewhat elevuted temperature, it sublimes in form of white 

 leaves, having the metallic lustre. If, on the other hand, the 

 selenium is in excess, it comes over first ; afterwards a subli- 

 mate rises which does not crystallize so well as the former, and 

 which either contains a mixture of selenium, oris a perseleniuret 

 easily decomposable by distillation. Then the white foliated 

 crystals make their appearance. 



Seleniuret. of mercury is but little attacked by nitric acid even 

 when boiling and concentrated. By long continued boiling, it 

 assumes the form of a white powder, which is a protoseleniate 

 of mercury, and the nitric acid contains selenic acid in solution. 

 If we separate the liquid, and then add muriatic acid, the white 

 powder becomes red, and is converted into selenium. The 

 muriatic acid dissolves the red oxide of mercury, which has been 

 peroxidized by the reduction of part of the selenic acid. The 



