Sodium metabisulfite is a chemical compound with the formula Na₂S₂O₅. It is also known as sodium pyrosulfite and sodium disulfite. Na₂S₂O₅ is an ionic compound containing the sodium cation (Na+) and the metabisulfite anion (S2O52-). In its standard state, sodium metabisulfite exists as a white or yellowish-white powder.

This compound has a faintly pungent odour similar to that of sulfur dioxide. It is important to note that sodium metabisulfite may induce allergic reactions in humans who are sensitive to sulfites.

Uses of Sodium Metabisulfite

Na₂S₂O₅ is one of the primary ingredients used in Campden tablets. It is also used to sanitize the equipment used for winemaking.

This compound is also used to increase the shelf life of several local anaesthetics.

Concentrated Na₂S₂O₅ can be used for the removal of tree stumps since it degrades the lignin in it.

Sodium sulfite is also used to test for sickle cell diseases.

When gold is dissolved in aqua regia, it can be precipitated out with the help of this compound.

Since it can act as an oxygen scavenger, Na2S2O5 is used as a corrosion inhibitor in the oil industry.

This compound is also used in the treatment of wastewater since it can reduce hexavalent chromium into its trivalent form.