"76 



METALS. 



that the selenium adheres to the membrane of the nos- 

 trils and trachea. The eyes are likewise affected with 

 inflammation when exposed to this gas. 



Seleniuretted hydrogen, according to the experi- 

 ments of Berzelius, is composed of 

 97.4 selenium, 

 2.6 hydrogen. 



This compound of selenium may be considered analo- 

 gous to sulphuretted hydrogen. 



No compound of selenium and carbon has yet been 

 fcirmed, though, from some experiments, it is conjec- 

 tured that these bodies do unite. 



rfifisjihuret of Selenium, is formed when selenium 

 and phosphorus are heated together. The compound 

 is fusible, and is of a dark colour, having a vitreous 

 fracture. When digested in water, it decemposes this 

 fluid; seleniuretted hydrogen is formed, and selenium 

 is deposited. 



Sulphurel of selenium may be procured by passing a 

 stream of sulphuretted hydrogen through a solution of 

 selenic acid, and then adding a few drops of muriatic 

 acid, by which thesulphuret of selenium is precipitated 

 of an orange colour. This compound is very fusible, 

 passing into the liquid state at a temperature a little 

 below that of boiling water. By the application of a 

 stronger heat it volatilizes, and again condenses of an 

 orange colour. Sulphuret of selenium, when heated 

 in the air, bums and emits the odour of sulphurous 

 acid, and of horse-raddish. When exposed to heat 

 with selenic acid, it is decomposed, and the sulphur 

 combines with the oxygen. 



This compound is not easily acted on by nitric 

 acid; nitro- muriatic acid, however, dissolves it. 

 Sulphuret of selenium is composed of 

 100 selenium, 



60.75 sulphur. 



Selenium, and the alkalies and earths. By the action 

 of selenium on the alkalies and earths, compounds are 

 formed, analogous to those generated by the action of 

 sulphur on these bodies. It is probable, therefore, 

 that they are compounds of the bases with seleniuret- 

 ted hydrogen, having the selenium in excess. If so, 

 they are Seleniuretted hydro-seleniurets. 



When aqua potassas is boiled on selenium, a solution 

 is formed, having the colour and odour of sulphuret- 

 ted hydro-sulphuret of potassa. The same compound 

 may be obtained by exposing to heat selenium and po- 

 tassa, or its sub-carbonate. 



When an acid is added to the solution of this sub- 

 stance, selenium is precipitated. 



Ammonia does not, either in the state of gas, or in 

 solution in water, act on selenium. 



When Seleniuretted hydro-seleniuret of lime and mu- 

 riate of ammonia are subjected to heat, a reddish-co- 

 loured fluid distils over, which, when exposed to the 

 air, emits ammonia, and deposits selenium. By the 

 addition of a large quantity of water to it, selenium is 

 also precipitated. There is left in the retort after the 

 distillation, muriate, seleniate, and hydro-seleniate of 

 lime. When selenium and lime are exposed to heat, 

 the two unite, and form a black substance destitute of 

 taste and smell, and insoluble in water. On the addi- 

 tion of an acid to this, the selenium is left in the form 

 of a spongy mass. This compound may be got crys- 

 tallized, by exposing to tire air a solution of hydro- 

 seleniuret of lime. The crystals appear to be four- 

 sided prisms, with truncated summits. 



The compounds formed with baryta, strontia, mag- 

 nesia, and alumina, are insoluble. By the addition of 



an acid to them the selenium is separated, and the two Metal. 

 last yield that metal on the application of heat. " ~Y~- 



Selenium and the metals. Selenium combines with 

 the metals, presenting with most of them the same 

 phenomena as sulphur. 



The seleniurets have in general a metallic aspect 

 and are usually more fusible than the metals which' 

 they contain. By the application of heat to them, the 

 selenium burns with a blue flame, emitting the odour 

 of horse-radish. 



Seleniuret of potassium. When selenium and potas- 

 sium are heated together, they combine, and during 

 their union emit caloric, sufficient to raise the temper- 

 ature of the compound to ignition, by which a portion 

 of selenium is sublimed. 



Seleniuret of potassium resembles iron in appearance, 

 having a crystalline structure. When thrown into 

 water, decomposition ensues, and hydro-seleniuret of 

 potassa is formed. The solution is of a reddish colour, 

 and possesses the property of keeping dissolved an ex- 

 cess of selenium, for when nitric acid is added to it, 

 selenium is deposited. 



When selenium is heated with an excess of potas- 

 sium, an explosion occurs, and the product is scattered 

 about by the potassium which is converted into va- 

 pour. The compound formed in this instance, when 

 put into water, is dissolved, and hydrogen is disen- 

 gaged. 



Seleniuret of iron may be procured by passing the 

 vapour of selenium over iron filings, at a high tempe- 

 rature; during the union, caloric is evolved. The 

 compound has a dark-grey colour, and metallic aspect. 

 It is hard and brittle, with a granular texture. When' 

 heated at the flame of a candle, part of the selenium is 

 volatilized. Seleniuret of iron, when acted on by mu- 

 riatic acid, affords Seleniuretted hydrogen. In this 

 case the first portion of gas disengaged is decomposed 

 by the air in the apparatus, and selenium is deposited, 

 which gives to the liquid a reddish colour. Along 

 with Seleniuretted hydrogen, another gaseous fluid is 

 given out, which has a disagreeable odour, is inflam- 

 mable, and is not dissolved by water, nor by the solu- 

 tions cf the alkalies. When passed through a solu- 

 tion of proto-nitrate of iron, a black precipitate is 

 thrown down. 



Selenium unites with a less proportion of iron, and 

 forms a compound not soluble in muriatic acid, and 

 which, by exposure to heat, parts with the excess of 

 selenium. 



Seleniuret of copper is formed by passing seleniuret- 

 ted hydrogen through a solution of copper, by which 

 a dark-grey substance is precipitated, which, on ex- 

 posure to heat, loses half of its selenium, and proto- 

 sulphate of copper is left behind. This compound 

 may also be procured by heating selenium and copper- 

 filings together. 



Seleniuret of lead. Selenium and lead unite with an 

 evolution of caloric. The Seleniuret is of a grey co- 

 lour, and porous. When heated before the blow-pipe 

 on charcoal, part of the selenium is oxidized, and sub- 

 seleniate of lead is formed, which is afterwards decom- 

 posed, and Seleniuret of lead is regenerated. 



Selenium unites with more lead, and forms a com- 

 pound less fusible than the former. 



Seleniuret of tin is of a grey colour, and possesses 

 the metallic lustre in a high degree. When exposed 

 to heat, the selenium is volatilized, and the tin is oxi- 

 dated. 



Seleniuret of zinc. When selenium and zinc ar 



