Sodium bisulfite

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.

Not to be confused with sodium bisulfate.
Sodium bisulfite
Names
IUPAC name
Sodium hydrogen sulfite
Other names
E222, sodium bisulphite
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.028.680
E number E222 (preservatives)
RTECS number
  • VZ2000000
UNII
Properties
NaHSO3
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/100 mL
1.526
Hazards
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R-phrases (outdated) R22 R31
S-phrases (outdated) (S2), S25, S46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 code
0
2
1
Flash point Non-flammable
NIOSH (US health exposure limits):
PEL (Permissible)
 none[1]
REL (Recommended)
 TWA 5 mg/m3[1]
IDLH (Immediate danger)
 N.D.[1]
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).
N verify (what is YN ?)
Infobox references

Synthesis

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
Further information: bisulfite
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

References
  1. 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.
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