Carbon Subselenides

Carbon Subselenides of compositions C₄Se and C₅Se₂ have been described. When amorphous red selenium is distilled with carbon tetrabromide, in the molecular proportions 2:1, the greyish-black residue obtained after treatment with carbon disulphide, phenol, alcohol and ether in succession, has the composition C₉Br₂Se₄. This substance when heated with a very concentrated solution of sodium hydroxide forms the selenide C₄Se, a compound which dissolves with difficulty in concentrated sulphuric acid to give a light brown solution. If the sodium hydroxide solution of the bromoselenide is treated with hydrochloric acid, a violet-brown precipitate of the compound C₅Se₂ is obtained, which readily dissolves in hot concentrated sulphuric acid to give a reddish- brown solution.

The phenol extract of the residue from the foregoing distillation, on boiling with aqueous alcohol gives a brown, flocculent precipitate, of composition C₁₀BrSe₅, and this when boiled with concentrated sodium hydroxide also yields the selenide C₅Se₂.

Other bromoselenides obtained by the interaction of selenium and carbon tetrabromide are stated to have the following compositions: C₃BrSe₃.3H₂O, red crystals with a metallic lustre, m.pt. 120° C.; C₃Br₂Se₂, orange-coloured solid, m.pt. 210° to 212° C.; C₂Br₂Se₄, brownish-red leaflets, m.pt. 154° C.