Chromic Selenide, Cr₂Se₃

This compound is produced as a maroon-coloured amorphous powder by heating the sesquioxide in selenium vapour and hydrogen or nitrogen; by the action of hydrogen selenide upon chromic chloride, it is obtained in the crystalline condition. The double selenide of potassium and chromium, K₂Cr₂Se₄, is prepared as dark green hexagonal crystals, which are readily soluble in nitric acid but insoluble in hydrochloric acid, by heating to redness a mixture of potassium cyanide, selenium, and chromic oxide.