Sodium metabisulfite

Chembox new
Name = Sodium Metabisulfite
ImageFile = Sodium metabisulfite.jpg
ImageName = Sodium metabisulfite
OtherNames = Sodium Pyrosulfite
Sodium Disulfite
Section1 = Chembox Identifiers
CASNo = 7681-57-4
Section2 = Chembox Properties
Formula = Na₂S₂O₅
MolarMass = 190.1 g/mol
Appearance = white powder
Density = 1100 to 1200 kg/m³ (solid)
Solubility = 65 (25 °C)
Solubility = 47 (20 °C)
MeltingPt = >170 °C (begins at 150)
BoilingPt =
Section7 = Chembox Hazards
EUClass =
NFPA-H = 2
NFPA-F = 0
NFPA-R = 2
NFPA-O = ox
RPhrases =
SPhrases =

Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E. sodium metabisulphite or sodium pyrosulphite) is an inorganic compound of chemical formula Na₂S₂O₅. The name is sometimes referred to as "disodium" (metabisulfite, etc). It is used as a disinfectant, antioxidant and preservative agent.

Uses

Food additive

It is used as a food additive, mainly as a preservative and is sometimes identified as E223.

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

It is present in many dilutable squashes (i.e. fruit juice concentrates) and in candy bars such as Mounds. [ [http://www.foodfacts.com/members/item_info.cfm?id=11076 FoodFacts.com ] ]

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 sulphate and excreted in the urine. [ [http://www.food-info.net/uk/e/e223.htm Food-Info.net : E-numbers : E223: Sodium disulphite ] ]

anitization / Cleaning agent

It is commonly used in homebrewing preparations to sanitize equipment. It is used as a cleaning agent for potable water reverse osmosis membranes in desalination systems. It is also used to remove chloramine from drinking water after treatment.

Other uses

Concentrated potassium metabisulfite can be used to remove tree stumps. The "Stump-Out" brand has 98% potassium metabisulfite, and causes degradation of lignin in the stumps, facilitating removal. [http://www.bonideproducts.com/labels/pdf/stump-out.pdf]

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

Chemical properties

When mixed with water, sodium metabisulfite releases sulfur dioxide (SO₂), a pungent, unpleasant smelling gas that can also cause breathing difficulties in some people. For this reason, sodium metabisulfite has fallen from common use in recent times, with agents such as hydrogen peroxide becoming more popular for effective and odorless sterilization of equipment. Released sulfur dioxide however makes the water a strong reducing agent.

References