Potassium Metabisulfite

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Infobox on Potassium Metabisulfite
Example of Potassium Metabisulfite
Potassium metabisulfite-1.jpg
Stowage factor (in m3/t)
Humidity / moisture
Risk factors

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. The product is soluble in water.


It is used as an antiseptic, reagent, source of sulphurous acid, brewing (cleaning casks and vats), wine-making (said to kill only undesirable yeasts and bacteria), food preservative, developing agent (photography), process engraving and lithography, dyeing, antioxidant, bleaching agent.

Shipment / Storage / Risk factors

Shipped in bottle or drums. Used as an antiseptic, as a food preservative, a bleaching agent in photography and in the brewing and wine-making industries.

On exposure, becomes damp, tinged with yellow, and undergoes a chemical change. For example, instead of containing the customary 54% to 57%, sulphur trioxide the damaged portion on analysis may be found to contain only 20% to 22%.

Appearance White crystalline powder
Odour Pungent (sulfur dioxide)
Density 2.34 g/cm 3 (solid
Melting point 190°C. decomp.
Solubility in water 450 g/l (20°C)
Solubility Insoluble in ethanol

Note: For overseas carriage aspects of Chemicals, the readers are recommended to acquire or have access to a good chemical dictionary, and a copy of the International Maritime Dangerous Goods (IMDG) Code, issued by the International Maritime Organisation. Also consult the applicable MSDS sheet.