Potassium metabisulfite

• Potassium metabisulfite, K2S2O5, also known as potassium pyrosulfite, 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 disulfite and is chemically very similar to sodium metabisulfite, with which it is sometimes used interchangeably. 
• Potassium metabisulfite is generally preferred out of the two as it does not contribute sodium to the diet.
• Potassium metabisulfite has a monoclinic crystal structure which decomposes at 190 °C, yielding potassium oxide and sulfur dioxide.