Also known as chromium trioxide or chromium oxide, with a molecular weight of 151.99. It is a hexagonal crystal, green powder. Insoluble in water, acids, and organic solvents, slightly soluble in concentrated sodium hydroxide solution, soluble in hot sodium bromate solution, hot concentrated perchloric acid solution, or boiling sulfuric-phosphoric mixed acid. Extremely stable to light, atmosphere, and corrosive gases (such as H2S, SO2, etc.), with excellent weather resistance. Stable when heated, with a melting point of 2265°C and a boiling point of 3000°C, making it a high-quality refractory material. Used for smelting metallic chromium and chromium carbide, coloring of enamel, ceramics, glass, artificial leather, refractory materials, and building materials, as a catalyst for organic synthesis, manufacturing light-resistant materials and special inks for printing banknotes, metal polishing and grinding materials, metal surface chromium infiltration, magnetic materials, etc. Used in coatings, ceramics, rubber, artist pigments, and camouflage coatings.