|Other names||Sodium Pyrosulfite|
|ECHA InfoCard||Lua error in Module:Wikidata at line 879: attempt to index field 'wikibase' (a nil value). Lua error in Module:Wikidata at line 879: attempt to index field 'wikibase' (a nil value).|
|Molar mass||190.1 g/mol|
|Density||1100 to 1200 kg/m³ (solid)|
|Except where noted otherwise, data are given for|
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references
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 sterilizer and antioxidant/preservative.
It is used as a food additive, mainly as a preservative and is sometimes identified as E223. As an additive, it may cause allergic reactions, particularly skin irritation e.g. eczema; gastric irritation and asthma. It is not recommended for consumption by children. It is present in many dilutable squashes (i.e. fruit juice concentrates) and in candy bars such as Mounds 
Sterilization / 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.
In the brand Stump-Out, it is used in almost a pure form (98%) to cause degradation of lignin, creating pores for fuel adsorption, and consequently, ignition.
It can be purchased in powdered form. Either sodium or potassium metabisulfite will be the primary ingredient in Campden tablets and some stump removers. In solid form it ranges in color from white to slightly yellow.
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.
Include ascorbates 300-304 in some applications. Calcium sulfate 516 and ascorbic acid 300 are safe alternatives to sodium metabisulfite used as a flour improver.
This article needs additional citations for verification. (September 2007) (Learn how and when to remove this template message)