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Sodium bisulfite

Chemical compound From Wikipedia, the free encyclopedia

Sodium bisulfite
Not to be confused with Sodium bisulfate.

Sodium bisulfite (or sodium bisulphite, sodium hydrogen sulfite) is a chemical mixture with the approximate chemical formula NaHSO3. Sodium bisulfite 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 appears in form of white or yellowish-white crystals with an odor of sulfur dioxide. Sodium bisulfite is used in a variety industries such as a food additive with E number E222 in the food industry. It is a reducing agent in the cosmetic and in the bleaching applications.[3][4][5]

Quick Facts Names, Identifiers ...
Sodium bisulfite
Thumb
Thumb
Ball-and-stick model of a bisulfite anion (left) and a sodium cation (right)
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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
  • InChI=1S/Na.H2O3S/c;1-4(2)3/h;(H2,1,2,3)/q+1;/p-1 Y
    Key: DWAQJAXMDSEUJJ-UHFFFAOYSA-M Y
  • InChI=1/Na.H2O3S/c;1-4(2)3/h;(H2,1,2,3)/q+1;/p-1
    Key: DWAQJAXMDSEUJJ-REWHXWOFAL
  • [Na+].[O-]S(=O)O
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
GHS labelling:
GHS07: Exclamation mark
H302
P301+P312+P330
NFPA 704 (fire diamond)
ThumbHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
2
0
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
Sodium biselenite
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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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 crystallize the product yield sodium metabisulfite (also called sodium disulfite), Na2S2O5.[6]

Upon dissolution of the metabisulfite in water, bisulfite is regenerated:

Na2S2O5 + H2O → 2 Na+ + 2 HSO3−

Sodium bisulfite is formed during the Wellman-Lord process.[7]

Uses

Cosmetics

Sodium bisulfite functions as a hair-waving/straightening agent.[8] As of 1998, sodium bisulfite was used in 58 cosmetic products including hair conditioners, moisturizers, and hair dyes.[9]

Food industry

Sodium bisulfite is used to prevent discoloration, bleach food starches, and delay spoilage of the product. In the US, EPA, FDA, and American Conference of Governmental Industrial Hygienists established a working place threshold limit value for sulfur dioxide of 2ppm averaged over 8 hours, and a 3-hour level of 5ppm. Even with this threshold established, the FDA recognized sodium bisulfite as "generally recognized as safe" compound.[3]

Sulfites in food can be assayed by the Monier-Williams type procedure,[10] HPLC after extraction, and Flow Injection analysis.[5]

Textile industry

Sodium bisulfite is used as an antichlor in the textile industry.[3][4] Antichlors are very useful in the textile industry because bleaching of compounds using chlorine is a standard practice.

Safety

Summarize
Perspective

The International Agency for Research on Cancer concluded that there was inadequate evidence that sodium bisulfite was carcinogenic.[3] Under specific conditions such as acidity and concentration level, sodium bisulfite was able to cause negative alterations to the genome such as catalyzing transamination, and to induce sister-chromatid exchanges suggesting possible genotoxicity.[11] In a study using Osbourne-Mendel strain rats, it was concluded that oral toxicity was not significant if the consumed concentration was less than 0.1% (615 ppm as SO2).[12] A study by Servalli, Lear, and Cottree in 1984 found that sodium bisulfite did not produce membrane fusion in hepatic and murine glial cells and human fibroblasts, so there is no oral toxicity. These clinical studies concluded that sodium bisulfite was safe to use in cosmetic formulations.[3]

The concentrations of sodium bisulfite that could be dangerous are well beyond the concentrations discussed in the cosmetic and food industry..[4][13]

The World Health Organization Expert Committee on Food Additives concluded that 0-0.7mg of sulfur dioxide equivalent/kg of body weight per day will cause no harm to an individual consuming this compound as a food additive. Sulfites exhibit no genotoxicity and carcinogenicity.[5]

See also

References

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