Sodium Metabisulfite (Food Grade) (CAS: 7681-57-4)

Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E.

sodium metabisulphite or sodium pyrosulphite) is an inorganic compound

of chemical formula Na2S2O5. The substance is sometimes referred to as

disodium (metabisulfite). It is used as a disinfectant, antioxidant and preservativeagent.

Uses

Food additive

It is used as a preservative and antioxidant in food and is also known as E223.

It may cause allergic reactions in those who are sensitive to sulfites, including

respiratory reactions in asthmatics, anaphylaxis and other allergic reactions in

sensitive individuals.

Sodium metabisulfite and potassium metabisulfite are the primary ingredients in

Campden tablets, used for wine and beer making.

The acceptable daily intake is up to 0.7 mg per kg of body weight. Sodium metabisulfite

has no side effects; it is oxidised in the liver to harmless sulfate and excreted in urine.

Other uses

Added to local anaesthetic (lidocaine etc.) solutions to prevent oxidation of vasoconstrictor

adrenaline and thus improve the shelflife of the solution

It is used in photography.

Concentrated sodium metabisulfite can be used to remove tree stumps. Some brands contain

98% sodium metabisulfite, and cause degradation of lignin in the stumps, facilitating removal.

It is also used as an excipient in some tablets, such as paracetamol. Approximately 0.5 mg

is used in epinephrine autoinjectors such as the EpiPen.

A very important health related aspect of this substance is that it can be added to a blood

smear in a test for sickle cell anaemia (and other similar forms of haemoglobin mutation).

The substances causes defunct cells to sickle (through a complex polymerisation)

hence confirming disease.

It is used as the source of SO2 in wine. An important anti-oxidant and bactericide

It is also used to precipitate gold from auric acid (gold dissolved in aqua regia).

It is used in waste treatment to chemically reduce hexavalent chromium to trivalent chromium

which can then be precipitated and removed from an aqueous waste stream.

It is used as a bleaching agent in the production of Coconut cream.

It is used as a SO2 source (mixed with air or oxygen) for the destruction of cyanide in

commercial gold cyanidation processes.