Sodium bisulfite

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Sodium bisulfite
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, sodium bisulphite
3D model (JSmol)
ECHA InfoCard 100.028.680 Edit this at Wikidata
E number E222 (preservatives)
RTECS number
  • VZ2000000
Molar mass 104.061 g/mol
Appearance White solid
Odor Slight sulfurous odor
Density 1.48 g/cm3
Melting point 150 °C (302 °F; 423 K)
Boiling point 315 °C (599 °F; 588 K)
42 g/100mL
Harmful (Xn)
R-phrases (outdated) R22 R31
S-phrases (outdated) (S2), S25, S46
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
NIOSH (US health exposure limits):
PEL (Permissible)
REL (Recommended)
TWA 5 mg/m3[1]
IDLH (Immediate danger)
Related compounds
Other anions
Sodium sulfite
Sodium metabisulfite
Other cations
Potassium bisulfite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sodium bisulfite (or sodium bisulphite, sodium hydrogen sulfite) is a chemical mixture with the approximate chemical formula NaHSO3. Sodium bisulfite in fact is not a real compound,[2] but a mixture of salts that dissolve in water to give solutions composed of sodium and bisulfite ions. It is a white solid with an odour of sulfur dioxide. Regardless of its ill-defined nature, "sodium bisulfite" is a food additive with E number E222.


Sodium bisulfite solutions can be prepared by treating a solution of suitable base, such as sodium hydroxide or sodium bicarbonate with sulfur dioxide.

SO2 + NaOH → NaHSO3
SO2 + NaHCO3 → NaHSO3 + CO2

Attempts to crystallise the product yield sodium disulfite, Na2S2O5.[3]

Reactivity and uses[edit]

A tank containing 25% sodium bisulfite at a water treatment plant in Sunnyvale, California.

Sodium bisulfite is a common industrial reducing agent, 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.

It is used for preserving food and beverages.

See also[edit]


  1. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0561". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ Tudela, David; Jenkins, H. Donald B. (2003). "New Methods to Estimate Lattice Energies: Application to the Relative Stabilities of Bisulfite (HSO3) and Metabisulfite (S2O52-) Salts". Journal of Chemical Education. 80 (12): 1482. Bibcode:2003JChEd..80.1482T. doi:10.1021/ed080p1482.
  3. ^ Johnstone, H. F. (1946). "Sulfites and Pyrosulfites of the Alkali Metals". Inorganic Syntheses. Inorganic Syntheses. 2. pp. 162–167. doi:10.1002/9780470132333.ch49. ISBN 9780470132333.