Characteristic

Potassium metabisulfite, K₂S₂O₅, also known as potassium pyrosulfite, is a white crystalline powder with a pungent odour. As a disulfite, it is chemically very similar to sodium metabisulfite, with which it is sometimes used interchangeably. Potassium metabisulfite has a monoclinic crystal structure.

Chemical formula:K₂S₂O₅

Molar mass:222.31 g·mol⁻¹

Appearance:White crystalline powder

Odor:Pungent (sulfur dioxide)

Density:2.34 g/cm³ (solid)

Melting point:190 °C (374 °F; 463 K) decomposes

Solubility in water:450 g/l (20 °C)

Solubility:Insoluble in ethanol

Application

It serves as a component of certain photographic developers and its solution is used in photographic fixing, in the textile industry for dyeing and cotton printing. It is utilized to precipitate gold from solution in aqua regia.