Hydrofluotitanic acid, H₂TiF₆

Hydrofluotitanic acid, H₂TiF₆, is not known in the pure state, but is formed in solution when titanic oxide is dissolved in aqueous hydrofluoric acid, the heat of solution being:

[Ti(OH)₄, 6HF, aq.] = 30,900 calories.

As a result of this reaction the solution increases in electric conductivity, since hydrofluotitanic acid is a much stronger acid than hydrofluoric acid.

Numerous titanifluorides are known which generally correspond to the type M'₂TiF₆ and are isomorphous with the silici-, zirconi-, and stanni-fluorides.

Titanifluorides differ from silicifluorides in their behaviour when heated with concentrated sulphuric acid; for, owing to the comparative non-volatility of titanium tetrafluoride this latter compound is not vaporised, as is silicon tetrafluoride from a silicifluoride under similar conditions, but the titanium is converted quantitatively into titanic oxide. On this account titanium tetrafluoride cannot be prepared by heating calcium fluoride and titanic oxide with sulphuric acid.

The titanifluorides are formed by the union of their component fluorides, and, like various other complex salts, are characterised by sparing solubility in water.