4.3 TITANIUM DIOXIDE (TiO2)
Titanium dioxide has its systematic name of Dioxotitanium. With its molecular formula of TiO2 and molecular weight of 79.87, it occurs in nature as well-known minerals rutile, anatase and brookite. Recently, Ries crater in Bavaria found two high pressure forms additionally, a monoclinic baddeleyite-like form and an orthorhombic α-PbO2-like form. But the most common form is rutile that is also the equilibrium phase at all temperatures. Titanium dioxide is insoluble in water and organic solvents, but slowly soluble in hydrofluoric acid and hot strong sulphuric acid. When you need to store it, it should be kept sealed in the cool, dry and well-ventilated place.
Pure titanium dioxide does not occur in nature but is derived from ilmenite or leuxocene ores. It is also readily mined in one of the purest forms, rutile beach sand. These ores are the principal raw materials used in the manufacture of titanium dioxide pigment. The first step is to purify the ore, and is basically a refinement step. Either the sulphate process, which uses sulphuric acid as an extraction agent or the chloride process, which uses chlorine, may achieve this. After purification the powders may be treated (coated) to enhance their performance as pigments.[