| 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. |