Chromium trioxide

Chromium trioxide (also known as chromium(VI) oxide or chromic anhydride) is the inorganic compound with the formula CrO3. It is the acidic anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a dark-purple solid. Millions of kilograms are produced annually, mainly for electroplating. Chromium trioxide is a powerful oxidiser, a mutagen, and a carcinogen. Chromium trioxide is generated by treating sodium dichromate with sulfuric acid: Approximately 100,000 tonnes are produced annually by this or similar routes. The solid consists of chains of tetrahedrally coordinated chromium atoms that share vertices. Each chromium center therefore shares two oxygen centers with neighbors. Two oxygen atoms are not shared, giving an overall stoichiometry of 1:3. The structure of monomeric CrO3 has been calculated using density functional theory, and is predicted to be pyramidal (point group C3v) rather than planar (point group D3h).