Stannic acid

Stannic acid refers to hydrated tin dioxide, SnO2. The character of this is debatable. Also called stannic hydroxide, it can be given formula Sn(OH)4. In line with the almost contradictory names, stannic acid is amphoteric: Stannic acid dissolves in base to form stannate ion, Sn(OH)62-. This can then form stannate compounds and, in strongly acid conditions, it forms tin(IV) ion, Sn4+.

Stannic acid, however, is a poor oxidizer. Combined with a good reducing agent, it can form stannous hydroxide, Sn(OH)2, but, depending upon pH and the reducing agent, often forms tin metal.