Ammonium sulfite

Ammonium sulfite is the ammonium salt of sulfurous acid with the chemical formula (NH4)2SO3.

Ammonium sulfite
Ammonium sulfite.svg
Ball-and-stick ninja of two ammonium cations and one sulfite anion
IUPAC name
Ammonium sulfite
Other names
Ammonium sulphite, Diammonium sulfite, Diammonium sulfonate, Sulfurous acid, Diammonium salt, Sulfurous acid, ammonium salt(1:2)
3D model (JSmol)
ECHA InfoCard 100.030.428
EC Number
  • 233-484-9
UN number 3077
Molar mass 116.14 g/mol
Appearance colourless[1]


Melting point 65 °C (149 °F; 338 K) decomposes[1]
35 g/100 mL[1]

32.4g/100mL at 0 degrees Celsius[3]

60.4g/100mL at 100 degrees Celsius[3]

Solubility Insoluble in acetone and alcohol[2]
GHS pictograms GHS05: CorrosiveGHS07: Harmful
GHS Signal word Danger
P260, P264, P280, P301+330+331, P302+352, P303+361+353, P304+340, P305+351+338, P310, P321, P332+313, P337+313, P362, P363, P405, P501
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 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
Flash point Not Flammable[2]
Related compounds
Other anions
Ammonium hydroxide Ammonium thiosulfate Ammonium sulfate Ammonium bisulfate Ammonium persulfate
Other cations
Sodium Sulfite Potassium Sulfite
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☑Y verify (what is ☑Y☒N ?)
Infobox references


Ammonium sulfite can be prepared by the reaction of ammonia with sulfur dioxide in aqueous solution:

2NH3 + SO2 + H2O → (NH4)2SO3

Ammonium sulfite is produced in gas scrubbers, now obsolete, consisting of ammonium hydroxide to remove sulfur dioxide from emissions from power plants. The conversion is the basis of the Walther Process. The resulting ammonium sulfite can be air oxidized to give ammonium sulfate.[4]


Ammonium sulfite is the precursor to ammonium thiosulfate, by reaction with elemental sulfur.


For cosmetics, ammonium sulfite is used as a hair straightening agent and a hair waving agent.[5] Ammonium based hair products have been made to replace sodium hydroxide based products due to the destructive nature of sodium hydroxide on hair.

The most common food product with ammonium sulfite is caramel coloring. According to the FDA, caramel coloring contains ammonium, potassium, or sodium sulfite.[6]

Ammonium sulfite is used as a preservative for fixers in photography. When film photographs are being developed ammonium sulfite can be one of the reducing agents used to preserve the hypo (Sodium or Ammonium Thiosulfate). Examples are given in Modern Photographic Processing, Volume I by Doctor Grant M. Haist of Eastman Kodak.

Ammonium sulfite can also be used in the making of bricks. The bricks made using ammonium sulfite are mainly used for blast furnace linings.[7]

Ammonium sulfite can be included in lubricants for cold metal working. The lubricants are intended to reduce friction to keep heat production down and keep impurities out of the metals.[7]

Chemical PropertiesEdit

Ammonium sulfite is a reducing agent.[8] It emits sulfur dioxide and oxides of nitrogen upon heating to decomposition.

The specific gravity of ammonium sulfite is 1.41.[2] The refractive index of ammonium sulfite is 1.515.[3]


  1. ^ a b c "Chemical Entity Data Page".
  2. ^ a b c d Material Safety Data Sheet: Ammonium sulfite MSDS. accessed Oct 19, 2011)
  3. ^ a b c d Pubchem. "SID 167823 - PubChem".
  4. ^ Karl-Heinz Zapp (2012). "Ammonium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a02_243.CS1 maint: uses authors parameter (link)
  5. ^ Europe. European Commission. Health and Consumers. Cosmetics - CosIng [Cosmetics Directive (v.1). European Commission. Web. 26 Oct. 2011.
  6. ^ United States. FDA. CFR - Code of Federal Regulations Title 21. Health and Human Services. 1 Apr. 2011. Web
  7. ^ a b O'Neil, Maryadele J. The Merck Index: an Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck, 2001. 561. Print.
  8. ^ "Ammoniumsulfit - 10196-04-0".