Tungsten blue, as known as blue tungsten oxide, BTO, β- tungsten oxide, hence the name as appearance of blue powder, with reducibility. Blue tungsten oxide refers to a class of dark blue compound with the mixed valence state of tungsten (Ⅵ) and tungsten (V), it is the product of the reducing agent and tungsten compound, its formula is WO3-x. The component of tungsten blue is indefinite, maybe coexist with tungsten trioxide, ammonium tungstate and tungsten dioxide, and the most common form is WO2.9, with its found density of 7.15g/cm3，X-ray density measurement of 7.16 g/cm3, and homogeneous area range of WO2.8975~2.9014(1000°C)。
Tungsten blue has a very complex composition, intermediate oxide of WO2, WO4 ect. can coexist. Tungsten blue if counted with t composition of WO2.9, then it has 82.13% of tungsten content, however, WO3澳门老永利总部 has 79.30% of W content.Tungsten blue generally formed in solution, may be made of tungsten oxide in hydrochloric acid suspension by zinc reduction in the system; or wet tungsten oxide by UV irradiation, and white gum tungstic acid in indirect sunlight; in addition, with a reducing agent, such as tin to reduce tungstate solution can also get "tungsten blue" to make the entire solution turning blue.