BdXXo, a green bud, on account of a brilliant green line in its spectrum) in the selenious mud of the sulphuric acid manufacture; the chemical affinities of this element, on the one hand approximating to the metals of the alkalis, and on the other hand to lead, were mainly established by C. A.
In this process, the residues are boiled with a dilute sulphuric acid to which nitric acid and potassium chlorate are added in order to transform the element into selenic acid, H 2 Se0 4, which is then reduced to selenious acid, H 2 Se0 3, by boiling with hydrochloric acid, and finally to selenium by sulphur dioxide.
Wehler (Ann., 1859, 109, p. 375) heats the well-washed chamber residues with potassium nitrate and carbonate in order to obtain an alkaline selenate, which is then boiled with hydrochloric acid, yielding selenious acid, from which the element is obtained as above; whilst H.
Ann., 1828, 90, p. 471) by the action of chlorine obtains selenium tetrachloride, which is converted into selenious acid by water, and the acid so prepared is finally reduced to selenium by treatment with sodium sulphite (see also G.
News, 1885, 5 1, p. 199) dissolves the element in boiling concentrated sulphuric acid and reduces the resulting selenious acid with sulphur dioxide, filters off the precipitate and washes it with water and alcohol.
The amorphous variety, which only differs from the vitreous form in its state of aggregation, is obtained by reducing solutions of selenious acid with sulphur dioxide.
A colloidal selenium was obtained by C. Paal and C. Koch (Ber., 1905, 38, p. 526) by reducing selenious acid dissolved in an aqueous solution of sodium protalbate with hydrazine hydrate and hydrochloric acid, the precipitate obtained being then dissolved in sodium carbonate.
It is decomposed by water with formation of selenium and selenious acid: 2Se 2 C1 2 +3H 2 0 = H2Se03-1-3Se Cl.
It dissociates when heated, and is decomposed by water with production of selenious acid.
Selenious acid, H 2 SeO 3, is obtained in the crystalline form when a solution of selenium dioxide in water is concentrated over sulphuric acid.
It is also obtained in the electrolysis of solutions of selenious acid (C. Manuelli and G.
A compound of selenium and sulphur has been described as resulting from the action of sulphuretted hydrogen on selenious acid, but A.