Ammonium sulfite is the

ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternar ...

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quanti ...

sulfurous acid Sulfurous acid (also sulfuric(IV) acid, sulphurous acid (UK), sulphuric(IV) acid (UK)) is the chemical compound with the formula . There is no evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase. ...

with the

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

(NH₄)₂SO₃.

Preparation

Ammonium sulfite can be prepared by the reaction of

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogeno ...

with

sulfur dioxide Sulfur dioxide ( IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic ...

aqueous solution An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would ...

: :2 NH₃ + 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 Ammonium sulfate (American English and international scientific usage; ammonium sulphate in British English); (NH4)2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitroge ...

Uses

Ammonium sulfite is the precursor to

ammonium thiosulfate Ammonium thiosulfate (ammonium thiosulphate in British English) is an inorganic compound with the formula . It is white crystalline solid with ammonia odor, readily soluble in water, slightly soluble in acetone and insoluble in ethanol and diethyl ...

, by reaction with elemental sulfur.

Niche

For cosmetics, ammonium sulfite is used as a hair straightening agent and a hair waving agent.Europe. European Commission. Health and Consumers. Cosmetics - CosIng [Cosmetics Directive (v.1)
European Commission. Web. 26 Oct. 2011. 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 Caramel color, E150d. According to the FDA, caramel coloring contains ammonium, potassium, or sodium sulfite.United States. FDA. CFR - Code of Federal Regulations Title 21. Health and Human Services. 1 Apr. 2011. Web
/ref> 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 thiosulfate Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula . Typically it is available as the white or colorless pentahydrate, . The solid is an efflorescent (loses water readily) crystalline substance that dissolves well ...

or ammonium thiosulfate). Ammonium sulfite can also be used in the making of bricks. The bricks made using ammonium sulfite are mainly used for blast furnace linings.O'Neil, Maryadele J. ''The Merck Index: an Encyclopedia of Chemicals, Drugs, and Biologicals''. Whitehouse Station, NJ: Merck, 2001. 561. Print. 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.

Chemical properties

Ammonium sulfite is a reducing agent. It emits sulfur dioxide and

oxides of nitrogen Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide * Nitrogen trioxide (), or n ...

upon heating to decomposition. The specific gravity of ammonium sulfite is 1.41.Material Safety Data Sheet: Ammonium sulfite MSDS. accessed Oct 19, 2011)
/ref> The refractive index of ammonium sulfite is 1.515.

References

{{Ammonium salts Ammonium compounds Sulfites