Sodium bisulfite

{{#if:104.061 g/molslight sulfurous odorslight sulfurous odorWhite solidNaHSO₃1.48 g/cm³42 g/100 mL1.526150|! style="background: #F8EABA; text-align: center;" colspan="2" | Properties

Sodium bisulfite
File:Sodium bisulfite.png
Ball-and-stick model of a bisulfite anion (left) and a sodium cation (right)
IUPAC name Sodium hydrogen sulfite
Other names E222
Identifiers
CAS number	7631-90-5 7pxY
PubChem	23665763
ChemSpider	571016 7pxY
ChEBI	CHEBI:26709 7pxY
ChEMBL	CHEMBL1689285 7pxN
RTECS number	VZ2000000
Jmol-3D images	Image 1
SMILES [Na+].[O-]S(=O)O <p><p style="word-wrap: break-word;">
InChI InChI=1S/Na.H2O3S/c;1-4(2)3/h;(H2,1,2,3)/q+1;/p-1 7pxY Key: DWAQJAXMDSEUJJ-UHFFFAOYSA-M 7pxY InChI=1/Na.H2O3S/c;1-4(2)3/h;(H2,1,2,3)/q+1;/p-1 Key: DWAQJAXMDSEUJJ-REWHXWOFAL
Molecular formula	NaHSO3
Molar mass	104.061 g/mol
Appearance	White solid
Odor	slight sulfurous odor
Density	1.48 g/cm3
Melting point	150 °C, 423 K, 302 °F
Solubility in water	42 g/100 mL
Refractive index (nD)	1.526
Hazards
EU Index	016-064-00-8
EU classification	Harmful (Xn)
R-phrases	R22 Template:R31
S-phrases	(S2), S25, S46
NFPA 704	75px 0 2 1
Flash point	Non-flammable
Related compounds
Other anions	Sodium sulfite Sodium metabisulfite
Other cations	Potassium bisulfite
14pxN (verify) (what is: 10pxY/10pxN?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium bisulfite (sodium hydrogen sulfite) is a chemical compound with the chemical formula NaHSO₃. Its most common use in oilfield is as an oxygen scavenger in seawater flood. Sodium bisulfite in contact with chlorine bleach (aqueous solution of sodium hypochlorite) will release harmful fumes. It also releases sulfur dioxide when mixed with acids.

It typically comes in 40wt% water solution and has a pH about 4.5 and specific gravity of 1.3-1.4.

Uses in chemistry

In organic chemistry sodium bisulfite has several uses. It forms a bisulfite adduct with aldehyde groups and with certain cyclic ketones to a sulfonic acid.

Bisulfite reaction

This reaction has limited synthetic value(s) but it is used in purification procedures. Contaminated aldehydes in a solution precipitate as the bisulfite adduct which can be isolated by filtration. The reverse reaction takes place in presence of a base such as sodium bicarbonate or sodium hydroxide and the bisulfite is liberated as sulfur dioxide.

Bisulfite adduct

Examples of such procedures are described for benzaldehyde, tetralone, citral, the ethyl ester of pyruvic acid and glyoxal. In the ring-expansion reaction of cyclohexanone with diazald, the bisulfite reaction is reported to be able to differentiate between the primary reaction product cycloheptanone and the main contaminant cyclooctanone.

The other main use of sodium bisulfite is as a mild reducing agent in organic synthesis in particular in purification procedures. It can efficiently remove traces or excess amounts of chlorine, bromine, iodine, hypochlorite salts, osmate esters, chromium trioxide and potassium permanganate.

A third use of sodium bisulfite is as a decoloration agent in purification procedures because it can reduce strongly coloured oxidizing agents, conjugated alkenes and carbonyl compounds.

Sodium bisulfite is also the key ingredient in the Bucherer reaction. In this reaction an aromatic hydroxyl group is replaced by an aromatic amine group and vice versa because it is a reversible reaction. The first step in this reaction is an addition reaction of sodium bisulfite to an aromatic double bond. The Bucherer carbazole synthesis is a related organic reaction.

Uses in food

While the related compound, sodium metabisulfite, is used in almost all commercial wines to prevent oxidation and preserve flavor, sodium bisulfite is sold by some home winemaking suppliers for the same purpose. In fruit canning, sodium bisulfite is used to prevent browning (caused by oxidation) and to kill microbes.

In the case of wine making, sodium bisulfite releases sulfur dioxide gas when added to water or products containing water. The sulfur dioxide kills yeasts, fungi, and bacteria in the grape juice before fermentation. When the sulfur dioxide levels have subsided (about 24 hours), fresh yeast is added for fermentation.

It is later added to bottled wine to prevent the formation of vinegar if bacteria are present, and to protect the color, aroma and flavor of the wine from oxidation, which causes browning and other chemical changes. The sulfur dioxide quickly reacts with oxidation by-products and prevents them from causing further deterioration.

Sodium bisulfite is also added to leafy green vegetables in salad bars and elsewhere, to preserve apparent freshness, under names like LeafGreen. The concentration is sometimes high enough to cause severe allergic reactions.

In the 1980s, sodium bisulfite was banned from use on raw fruits and vegetables in the United States following the deaths of 13 people who unknowingly consumed produce treated with excessive amounts of the substance.

Industrial uses

Sodium bisulfite is a common reducing agent in the chemical industries. As it readily reacts with dissolved oxygen:

2 NaHSO₃ + O₂ → 2 NaHSO₄

It is usually added to large piping systems to prevent oxidative corrosion. In biochemical engineering applications, it is helpful to maintain anaerobic conditions within a reactor. Sodium bisulfite should not be confused with sodium bisulfate which is used as a pH lowering chemical for swimming pools.

In wastewater treatment, sodium bisufite is often added following disinfection with a chlorine solution to neutralize the residual chlorine before discharging the treated effluent.

Storage

316-L stainless steel, polyethylene and fiberglass can be used safely to store Sodium Bisulfite Solution