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 seleniuretted hy drogen, having the selenium in excess. If so, they are seleniuretted hydro-seleniurets.
When aqua potassx is boiled on selenium, a solution is formed, having the colour and odour of sulphuretted hydro-sulphuret of potassa. The same compound may be obtained by exposing to heat selenium and potassa, or its sub-carbonate.
When an acid is added to the solution of this substance, 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-colour ed 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 pre cipitated. There is left in the retort after the distilla tion, muriate, seleuiate, 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 addition of an acid to this, the selenium is left in the form of a spongy mass. Tnis compound may be got crystallized, by ex posing to the air a solution of hydro seleniuret of lime. The crystals appear to be four-sided prisms, with trun cated summits.
The compounds formed with baryta,strontia, magnesia, and alumina, are insoluble. By the addition of an acid to them the selenium is separated, and the two last yield that metal on the application of heat.
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-raddish.
Seleniuret of fiotassium.—W hen selenium and potas sium are heated together, they combine, and during their union emit caloric. sufficient to raise the tempe rature 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 po tassa 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, se lenium 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 vapour. The compound formed in this instance, when put into water, is dissolved, and hydrogen is disengaged.
Seleniuret of iron may he 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. Scleniuret 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 infl.m mable, and is not dissolved by water, nor by the solu tions of the alkalies. When passed through a solution of proto-nit•ate 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 se lenium.