White powder. A soft and odorless white powder with strong covering and coloring power, with a melting point of 1560-1580 ℃. Insoluble in water, dilute inorganic acids, organic solvents, oil, slightly soluble in alkali, soluble in concentrated sulfuric acid. It turns yellow when exposed to heat, and then turns white again after cooling. Rutile type (R-type) has a density of 4.26g/cm3 and a refractive index of 2.72. R-type titanium dioxide has good weather resistance, water resistance, and is not prone to yellowing, but its whiteness is slightly poor. Sharp titanium type (Type A) has a density of 3.84g/cm3 and a refractive index of 2.55. A-type titanium dioxide has poor light resistance and is not resistant to weathering, but has good whiteness. In recent years, it has been discovered that nanoscale ultrafine titanium dioxide (usually 10-50 nm) has semiconductor properties, high stability, transparency, activity, dispersion, non toxicity, and color effect.