Potassium metabisulphite, K2S2O5, also known as potassium pyrosulphite, is a white crystalline powder with a pungent sulfur odour. The main use for the chemical is as an antioxidant or chemical sterilant. It is a disulphite and is chemically very similar to sodium metabisulphite, with which it is sometimes used interchangeably.
