Tungsten dioxide is also known as brown tungsten oxide, which is named as it appears as brown monoclinic system crystalline powder. It is the chemical compound with the formula WO2, a density of 10.82~11.05g/cm³. CAS No. is 12036-22-5. WO2 is soluble in concentrated sulfuric acid, but is insoluble in water, hydrochloric acid, dilute sulfuric acid and alkali solution. Because WO2 is unstable and easily oxidized to tungsten trioxide in the air, it is usually used to prepare tungsten trioxide and…