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 expo sure to heat, loses hair of its selenium. and proto•sul phate 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 colour, and porous. When heated before the blow-pipe on charcoal, part of the selenium is oxidized, and sub-se leniate of lead is formed, which is afterwards decompos ed, 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 oxida ted.
Seleniuret of zinc.—When selenium and zinc are heated together, the melted selenium covers the surface of the zinc, but docs not combine with it. If the heat be increased much above the fusing point, the former is volatilized, and the latter remains covered with a yellow pellicle.
When zinc, at an elevated temperature, is introduced into the vapour of selenium, an explosion occurs, and the vessel is lined with a lemon-coloured powdery sub stance, which is seleniuret of zinc. This is soluble in nitric acid, with the disengagement of nitric oxide.
Seleniuret of mercury.—When selenium and mercury are heated together, a substance resembling tin is form ed. If mercury be in excess, this is expelled, when the compound is subjected to heat ; the seleniuret then sublimes without fusing, and condenses in the form of white leaves, having a metallic lustre. Seleniuret of mercury is not easily acted on by nitric acid. When this is boiled on it, proto-seleniate of mercury is formed, and the nitric acid contains selenic acid. If mui iatic acid be poured on the seleniate, selenium is precipitated; the oxygen of the selenic acid passing to the mercury, by which the red oxide is generated. Seleniuret of mercury is soluble in nitro-muriatic acid.
Seleniuret of antimony has a metallic lustre and a crystalline appearance.
Seleniuret of arsenic.—'\Vhen arsenic is put into fused
selenium, the two metals unite, and a black mass is pro duced, which, when heated to redness, boils, and a sub limate is formed, which appears to be per-seleniuret of arsenic.
Seleniuret of platinum.—Platinum in powder, and se lenium, readily combine with the extrication of caloric, and generate a grey substance, which, when subjected to heat, parts with the selenium, and leaves the platinum. On this account the seleniates act readily on a platinum crucible.
Seleniuret of palladium is of a grey colour, and before the blow-pipe emits part of the selenium.
Seleniuret of bismuth has a silvery colour and metallic lustre, and requires a red heat for its fusion.
Seleniuret of tellurium is fusible, and sublimes in the form of a metallic mass—it is also oxidated, and gene rates seleniate of tellurium.
Selenic Acid and Bases.
The affinity of selenic acid for the bases seems to be below that of arsenic acid. The neutral seleniates are either insoluble, or sparingly soluble in water. Ber7e lius asserts that the acid of them contains just as much oxygen as exists in the base. The quantity of oxygen in a base sufficient to saturate 100 of acid is 14.37.
Selenic acid forms two classes of super-salts ; the first contains twice as much acid as exists in the neutral compounds, of course there is four times the quantity of oxygen that there is in the base. These salts Berze lius calls bi seleniates. The other super-salts appear to contain four times the acid of the neutral compound ; they are therefore termed quadri-seleniates.
Selenic acid forms also sub-salts with the alkalies, and with some of the metals. The alkaline seleniates have a saline taste. Those, with the earths and the metals, possess in general the taste of the base.
The compounds of selenic acid are decomposed by heat, which seems to be occasioned by their containing foreign inflammable matter. The same occurs when the seleniate of an alkali or earth is heated with char coal. Carbonic acid and carbonic oxide are formed, and a small quantity of selenium sublimes. When a metal lic seleniate is treated in this way, the selenium unites with the metal of the base, and forms a seleniuret.