Titanium Sesquioxide, Ti₂O₃

Titanium Sesquioxide, Ti₂O₃, is formed, probably in an impure state, when the dioxide is ignited strongly in a current of hydrogen, and is obtained in the form of lustrous, copper-coloured crystals, together with the trichloride and oxychloride, when a mixture of hydrogen and titanium tetrachloride vapour is passed over the white-hot dioxide.

When a microcosmic bead containing titanic oxide is heated in the reducing flame crystals of the sesquioxide separate.

This oxide is isomorphous with Elba haematite; and titanium iron ore, FeTiO₃, is on this account sometimes regarded as an isomorphous mixture of iron and titanium sesquioxides.

Titanium sesquioxide dissolves in concentrated sulphuric acid, forming a violet solution of the corresponding sulphate. The hydrated sesquioxide, Ti₂O₃.xH₂O, precipitated from a solution of the trichloride by alkali, may be black, red, brown, or dark blue. When suspended in water it constitutes a powerful reducing agent, even decomposing water, and being oxidised to the hydrated dioxide. When the hydrated sesquioxide is suspended in milk of lime and shaken with air, its oxidation is accompanied by an equivalent oxidation of water to hydrogen dioxide. A similar reaction occurs when chromic acid is added to titanium sesquioxide in presence of potassium iodide, the formation of titanic acid being accompanied by the liberation of an equivalent of iodine.