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It has already been seen that titanic hydroxide is amphoteric, dissolving in strong acids to form salts of these acids, and in strong alkalis to form titanates. Titanic hydroxide is thus an acid of the weakest description, and is unable to displace carbonic acid from aqueous solutions of carbonates. Alkali titanate, however, is formed when titanic oxide is fused with alkali carbonate, and the reaction is reversible when the fusion is carried out in an atmosphere of carbon dioxide, the conditions of equilibrium at 900°-1100° C. and 1 atmosphere CO2 being represented by the following equations:

0.29 Na2CO3 + 0.29TiO2 ⇔ 0.71 Na2TiO3 + xCO2
0.65 K2CO3 + 0.65TiO2 ⇔ 0.35 K2TiO3 + xCO2.

Titanic oxide resembles silica in its power of displacing carbon dioxide, and this power diminishes through zirconium to thorium with increase in the basic power of the dioxide.

Certain mineral titanates are known, and can be prepared artificially.

Perofskite is calcium metatitanate, CaTiO3, containing small quantities of ferrous, manganese, and magnesium oxides; it occurs in the Urals and Arkansas in yellow to iron-black rhombic crystals, having a density of 4.0 and hardness 5.5 on Moh's scale, and can be produced artificially by the strong ignition of a mixture of titanic oxide, lime, and potassium carbonate.

Ilmenite or titanic iron is ferrous metatitanate, FeTiO3; it occurs in Norway, Canada, and elsewhere in black rhombohedral crystals, having a sub-metallic lustre, density 4.5 to 5, and hardness 5 to 6 (Moh's scale).

Pyrophanite, isomorphous with ilmenite, is MnTiO3, and geikielite is MgTiO5.

Pseudobrookite is ferric orthotitanate, Fe4(TiO4)3; it consists of brown or black orthorhombic crystals of density 4.39 and hardness 6 (Moh's scale).

Titanite or sphene, calcium titanisilicate, CaTiSiO5, may be regarded as the calcium salt of dimetasilicic acid, H2Si2O5, in which a molecule of silica has been exchanged for one of titanic oxide. It occurs, embedded in granite, gneiss, and mica-schist, in yellow, green, red, grey, brown, or black monoclinic crystals of density 3.54 and hardness 5 to 5.5 (Moh's scale). It has been obtained artificially by fusing together a mixture of silica, titanic oxide, and calcium chloride.

Titanic oxide is known partially to replace silica in such minerals as biotite, augite, and olivine; and, according to Groth, the oxides ZrO2, ThO2, and SnO2 may also replace silica isomorphously. Neither titanic oxide nor any of these other oxides is known, however, to form such complex acids as are formed by silica.

Alkali titanates may be prepared by fusion, by boiling titanic acid with aqueous alkali, or by precipitating a hydrochloric acid solution of titanic acid with alkali carbonate. Thus potassium metatitanate, K2TiO3, is obtained as a yellow, fibrous mass when titanic oxide is fused with potassium carbonate; the hydrated salt K2TiO3.4H2O crystallises on evaporating a solution of titanic acid in caustic potash; the trititanate K2Ti3O7.2H2O is precipitated by potassium carbonate from a hydrochloric acid solution of titanic acid, whilst K2Ti3O7.3H2O is formed when K2TiO3 is boiled with water, and the hexatitanate K2Ti6O13.2H2O is produced by the action of hydrochloric acid on the dihydrated trititanate.

The three sodium salts, Na2Ti2O5, Na2Ti3O7, Na4Ti3O8, all of which are crystalline but insoluble in water, are produced by the fusion of titanic oxide with sodium carbonate, together with sodium tungstate, to promote crystallisation, and treatment of the cooled product with water.

In addition to these alkali salts and artificial minerals, a number of meta-, ortho-, and poly-titanates of other metals have been prepared, generally by fusing titanic oxide with the' carbonate, chloride, or sulphate of the metal. They are as follow: Sr2Ti3O8, Ba2Ti3O8, Mg2TiO4, MgTiO3, Zn2TiO4, ZnTiO3, ZnTi3O7, Zn3Ti2O7, Zn4Ti5O14, Mn2TiO4, MnTiO3, CoTiO3, NiTiO3, Fe2TiO4, FeTiO3.

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