Sodium Metabisulfite
General
Other names	Sodium Pyrosulfite Sodium Disulfite
Molecular formula	Na2S2O5
Molar mass	190.1 g/mol
Appearance	white powder
CAS number	7681-57-4
Properties
Density and phase	1100 to 1200 kg/m³, solid
Solubility in water	65 g/100 ml (25 °C)
Solubility in water	47 g/100 ml (20 °C)
Melting point	>170 °C (begins at 150)
Boiling point
Hazards
MSDS	External MSDS
EU classification
NFPA 704	0 2 2 ox
R-phrases
S-phrases
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Structural formula of sodium metabisulfite

Sodium metabisulfite or sodium pyrosulfite (American spelling; English spelling is 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. Image File history File links No higher resolution available. ... This article or section does not cite any references or sources. ... This article does not cite any references or sources. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: ρ (rho) is the density of the substance, measured in kg·m-3 m is the mass of the substance, measured in kg V is... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... Solubility refers to the ability for a given substance, the solute, to dissolve in a solvent. ... This article describes water from a scientific and technical perspective. ... Solubility refers to the ability for a given substance, the solute, to dissolve in a solvent. ... This article describes water from a scientific and technical perspective. ... The melting point of a crystalline solid is the temperature at which it changes state from solid to liquid. ... Italic text This article is about the boiling point of liquids. ... An example MSDS in a US format provides guidance for handling a hazardous substance and information on its composition and properties. ... Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (as amended) is the main European Union law concerning chemical safety. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... Image File history File links NFPA_704. ... R-phrases are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous substances and preparations. ... S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... Image File history File links Size of this preview: 800 × 415 pixelsFull resolution (1100 × 571 pixel, file size: 31 KB, MIME type: image/png) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 800 × 415 pixelsFull resolution (1100 × 571 pixel, file size: 31 KB, MIME type: image/png) File historyClick on a date/time to view the file as it appeared at that time. ... The structural formula of a chemical compound is a graphical representation of the molecular structure showing how the atoms are arranged. ... Traditionally, inorganic compounds are considered to be of mineral, not biological, origin. ... Space-filling model of the antioxidant metabolite glutathione. ... This article does not cite any references or sources. ...

Uses

Food additive

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, gastric irritation and asthma. It is not recommended for consumption by children.

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. It has been suggested that this article or section be merged with Homebrewing beer. ... Disinfection is the destruction of pathogenic and other kinds of microorganisms by physical or chemical means. ... Reverse osmosis is a separation process that uses pressure to force a solvent through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. ... Shevchenko BN350 desalination unit situated on the shore of the Caspian Sea. ... Chloramine (monochloramine) is chemical compound with the formula NH2Cl. ...

Stump Removing

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.^[1]

Oxidizer

Sodium metabisulfite has a moderate oxygen content by weight, approximately 42% (79.997amu/190.09654amu), so it is similar in oxygen content to potassium nitrate (KNO₃), which has approx. 47%. In potency, the potassium is more bound to the nitrogen than sodium is with sulfur, but the oxygens are less bound to the N as it is less reactive than sulfur with oxygen, so the potency would be comparable (for oxygenation). However, the density of sodium metabisulfite is only 1.1-1.2 g./cm³ compared to 2.11, which would have increased surface area for the same weight at same granulation size. Sulfur would need to be taken into account for this use, as it forms sulfur dioxide with degradation. R-phrases   S-phrases   Supplementary data page Structure and properties n, εr, etc. ...

Packaging

It can be purchased in powdered form, and is also the primary ingredient in campden tablets and some stump removers. In solid form it ranges in color from white to slightly yellow. Campden Tablets (Potassium or Sodium Metabisulfite) are a Sulphur based product that is used primarily in winemaking and beer-making to kill certain bacteria and to inhibit the growth of most wild yeast: this product is also used to eliminate both free chlorine, and the more stable form, chloramine, from...

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 sterlization of equipment. Released sulfur dioxide however makes the water a strong reducing agent. Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ...

SAFE ALTERNATIVES

Include ascorbates 300-304 in some applications. Calcium sulphate 516 and ascorbic acid 300 are safe alternatives to sodium metabisulphite used as a flour improver.

Sources

[1] http://www.bonideproducts.com/products/stumpout.htm (has MSDS sheet)

External links

• BASF AG's Chemical factsheet on Sodium Metabisulfite