Sodium sulfite

Last updated
Sodium sulphite
Na2SO3.svg
Sodium sulfite.jpg
anhydrous
Sodium sulfite hydrate.jpg
hydrate
Names
IUPAC name
Sodium sulfite
Other names
  • Hypo clear (photography)
  • E221
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.028.929 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 231-821-4
E number E221 (preservatives)
PubChem CID
RTECS number
  • WE2150000
UNII
  • InChI=1S/2Na.H2O3S/c;;1-4(2)3/h;;(H2,1,2,3)/q2*+1;/p-2 Yes check.svgY
    Key: GEHJYWRUCIMESM-UHFFFAOYSA-L Yes check.svgY
  • InChI=1/2Na.H2O3S/c;;1-4(2)3/h;;(H2,1,2,3)/q2*+1;/p-2
    Key: GEHJYWRUCIMESM-NUQVWONBAK
  • [O-]S(=O)[O-].[Na+].[Na+]
Properties
Na2SO3
Molar mass 126.043 g/mol
AppearanceWhite solid
Odor Odorless
Density 2.633 g/cm3 (anhydrous)
1.561 g/cm3 (heptahydrate)
Melting point 33.4 °C (92.1 °F; 306.5 K) (dehydration of heptahydrate)
500 °C (anhydrous)
Boiling point Decomposes
27.0 g/100mL water (20 °C)
Solubility Soluble in glycerol
Insoluble in ammonia, chlorine
log P −4
Acidity (pKa)~9 (heptahydrate)
1.565
Structure
Hexagonal (anhydrous)
Monoclinic (heptahydrate)
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 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 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Flash point Non-flammable
Safety data sheet (SDS) ICSC 1200
Related compounds
Other anions
Sodium selenite
Other cations
Potassium sulfite
Related compounds
Sodium bisulfite
Sodium metabisulfite
Sodium sulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Sodium sulfite (sodium sulphite) is the inorganic compound with the chemical formula Na2 SO3. A white, water-soluble solid, it is used commercially as an antioxidant and preservative. It is also suitable for the softening of lignin in the pulping and refining processes of wood and lignocellulosic materials. [1] A heptahydrate is also known but it is less useful because of its greater susceptibility toward oxidation by air. [2]

Contents

Preparation

Structure of anhydrous sodium sulfite Sodium-sulfite-xtal-3x3x3-c-3D-bs-17.png
Structure of anhydrous sodium sulfite

Sodium sulfite can be prepared by treating a solution of sodium hydroxide with sulfur dioxide. When conducted in warm water, Na2SO3 initially precipitates as a white solid. With more SO2, the solid dissolves to give the disulfite, which crystallizes upon cooling. [2]

Sodium sulfite is made industrially by treating sulfur dioxide with a solution of sodium carbonate. [3] The overall reaction is:

Uses

Sodium sulfite is primarily used in the pulp and paper industry. [4] It has been also applied in the thermomechanical conversion of wood to fibres (defibration) for producing medium density fibreboards (MDF). [5]

As an oxygen scavenger agent, it is used to treat water being fed to steam boilers to avoid corrosion problems, [6] in the photographic industry, it protects developer solutions from oxidation and (as hypo clear solution) to wash fixer (sodium thiosulfate) from film and photo-paper emulsions.

As a reducing agent it is used in the textile industry as a bleaching, desulfurizing, and dechlorinating agent (e.g. in swimming pools). Its reducing properties are exploited in its use as a preservative to prevent dried fruit from discoloring, and for preserving meats.

It is used as a reagent in sulfonation and sulfomethylation agent. It is used in the production of sodium thiosulfate.

The Wellman–Lord process utilizes sodium sulfite for flue gas desulfurization.

Reactions

Sodium sulfite is primarily used as a mild reducing agent. The heptahydrate crystals effloresce in warm dry air. Heptahydrate crystals also oxidize in air to form sodium sulfate. The anhydrous form is more resistant to oxidation by air. [7]

Sodium bisulfite, NaHSO3, is mixture of salts that dissolve in water to give solutions composed of sodium and bisulfite ions.

Structure

According to X-ray crystallography sodium sulfite heptahydrate features pyramidal SO32- centers. The S-O distances are 1.50 and the O-S-O angles are near 106º. [8]

Related Research Articles

<span class="mw-page-title-main">Sulfurous acid</span> Chemical compound

Sulfuric(IV) acid, also known as sulfurous (UK: sulphurous) acid and thionic acid, is the chemical compound with the formula H2SO3.

<span class="mw-page-title-main">Sulfite</span> Oxyanion with a central atom of sulfur surrounded by 3 oxygen atoms

Sulfites or sulphites are compounds that contain the sulfite ion, SO2−
3
. The sulfite ion is the conjugate base of bisulfite. Although its acid is elusive, its salts are widely used.

<span class="mw-page-title-main">Sodium metabisulfite</span> Chemical compound

Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E. sodium metabisulphite or sodium pyrosulphite) is an inorganic compound of chemical formula Na2S2O5. The substance is sometimes referred to as disodium metabisulfite. It is used as a disinfectant, antioxidant, and preservative agent. When dissolved in water it forms sodium bisulfite.

<span class="mw-page-title-main">Sodium thiosulfate</span> Chemical compound

Sodium thiosulfate is an inorganic compound with the formula Na2S2O3·(H2O)x. Typically it is available as the white or colorless pentahydrate, which is a white solid that dissolves well in water. The compound is a reducing agent and a ligand, and these properties underpin its applications.

<span class="mw-page-title-main">Flue-gas desulfurization</span> Technologies used in fossil-fuel power plants

Flue-gas desulfurization (FGD) is a set of technologies used to remove sulfur dioxide from exhaust flue gases of fossil-fuel power plants, and from the emissions of other sulfur oxide emitting processes such as waste incineration, petroleum refineries, cement and lime kilns.

In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. The reverse of disproportionation, such as when a compound in an intermediate oxidation state is formed from precursors of lower and higher oxidation states, is called comproportionation, also known as symproportionation.

<span class="mw-page-title-main">Sodium dithionite</span> Chemical compound

Sodium dithionite is a white crystalline powder with a sulfurous odor. Although it is stable in dry air, it decomposes in hot water and in acid solutions.

<span class="mw-page-title-main">Sodium dithionate</span> Chemical compound

Sodium dithionate Na2S2O6 is an important compound for inorganic chemistry. It is also known under names disodium dithionate, sodium hyposulfate, and sodium metabisulfate. The sulfur can be considered to be in its +5 oxidation state.

<span class="mw-page-title-main">Bisulfite</span> Chemical compound or ion

The bisulfite ion (IUPAC-recommended nomenclature: hydrogensulfite) is the ion HSO
3
. Salts containing the HSO
3
ion are also known as "sulfite lyes". Sodium bisulfite is used interchangeably with sodium metabisulfite (Na2S2O5). Sodium metabisulfite dissolves in water to give a solution of Na+HSO
3
.

<span class="mw-page-title-main">Potassium metabisulfite</span> Chemical compound

Potassium metabisulfite, K2S2O5, also known as potassium pyrosulfite, is a white crystalline powder with a pungent odour. It is mainly used as an antioxidant or chemical sterilant. As a disulfite, it is chemically very similar to sodium metabisulfite, with which it is sometimes used interchangeably. Potassium metabisulfite has a monoclinic crystal structure.

<span class="mw-page-title-main">Dithionite</span> Anion

The dithionite is the oxyanion with the formula [S2O4]2−. It is commonly encountered as the salt sodium dithionite. For historical reasons, it is sometimes called hydrosulfite, but it contains no hydrogen and is not a sulfite. The dianion has a steric number of 4 and trigonal pyramidal geometry.

<span class="mw-page-title-main">Potassium bisulfite</span> Chemical compound

Potassium bisulfite (or potassium hydrogen sulfite) is a chemical mixture with the approximately correctly mentioned formula chemical formula KHSO3. Potassium bisulfite in fact is not a real compound, but a mixture of salts that dissolve in water to give solutions composed of potassium ions and bisulfite ions. It is a white solid with an odor of sulfur dioxide. Attempts to crystallize potassium bisulfite yield potassium metabisulfite, K2S2O5.

The sulfite process produces wood pulp that is almost pure cellulose fibers by treating wood chips with solutions of sulfite and bisulfite ions. These chemicals cleave the bonds between the cellulose and lignin components of the lignocellulose. A variety of sulfite/bisulfite salts are used, including sodium (Na+), calcium (Ca2+), potassium (K+), magnesium (Mg2+), and ammonium (NH4+). The lignin is converted to lignosulfonates, which are soluble and can be separated from the cellulose fibers. For the production of cellulose, the sulfite process competes with the Kraft process which produces stronger fibers and is less environmentally costly.

<span class="mw-page-title-main">Calcium sulfite</span> Chemical compound

Calcium sulfite, or calcium sulphite, is a chemical compound, the calcium salt of sulfite with the formula CaSO3·x(H2O). Two crystalline forms are known, the hemihydrate and the tetrahydrate, respectively CaSO3·½(H2O) and CaSO3·4(H2O). All forms are white solids. It is most notable as the product of flue-gas desulfurization.

<span class="mw-page-title-main">Calcium bisulfite</span> Chemical compound

Calcium bisulfite is an inorganic compound which is the salt of a calcium cation and a bisulfite anion. It may be prepared by treating lime with an excess of sulfur dioxide and water. As a food additive it is used as a preservative under the E number E227. Calcium bisulfite is an acid salt and behaves like an acid in aqueous solution. It is used in the sulfite process for producing paper from wood chips.

The Wellman–Lord process is a regenerable process to remove sulfur dioxide from flue gas without creating a throwaway sludge product.

<span class="mw-page-title-main">Disulfite</span> Chemical compound

A disulfite, commonly known as metabisulfite or pyrosulfite, is a chemical compound containing the ion S
2
O2−
5
. It is a colorless dianion that is primarily marketed in the form of sodium metabisulfite or potassium metabisulfite. When dissolved in water, these salts release the hydrogensulfite HSO
3
anion. These salts act equivalently to sodium hydrogensulfite or potassium hydrogensulfite.

<span class="mw-page-title-main">Ammonium sulfite</span> Chemical compound

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

<span class="mw-page-title-main">Sodium bisulfite</span> Chemical compound

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, 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. Regardless of its ill-defined nature, sodium bisulfite is used in many different industries such as a food additive with E number E222 in the food industry, a reducing agent in the cosmetic industry, and a decomposer of residual hypochlorite used in the bleaching industry.

The topic of sulfite food and beverage additives covers the application of sulfites in food chemistry. "Sulfite" is jargon that encompasses a variety of materials that are commonly used as preservatives or food additive in the production of diverse foods and beverages. Although sulfite salts are relatively nontoxic, their use has led to controversy, resulting in extensive regulations. Sulfites are a source of sulfur dioxide (SO2), a bactericide.

References

  1. "High Yield Pulp Production by Modified Sulfite Process" (PDF). Retrieved 2023-10-19.
  2. 1 2 Johnstone, H. F. (1946). "Sulfites and Pyrosulfites of the Alkali Metals". Inorganic Syntheses. Vol. 2. pp. 162–167. doi:10.1002/9780470132333.ch49. ISBN   9780470132333.
  3. Weil, Edward D.; Sandler, Stanley R. (1999). "Sulfur Compounds". In Kroschwitz, Jacqueline I. (ed.). Kirk-Othmer Concise Encyclopedia of Chemical Technology (4th ed.). New York: John Wiley & Sons, Inc. p. 1937. ISBN   978-0471419617.
  4. Barberá, José Jiménez; Metzger, Adolf; Wolf, Manfred (2000). "Sulfites, Thiosulfates, and Dithionitesl Chemistry". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a25_477. ISBN   3527306730.
  5. "DE19958756A1 - Production of light-colored medium-density fibreboard (MDF) from old fibreboard comprises treatment with sodium sulfite, conversion into pulp and feeding into the blow-line of an MDF plant". Google Patents. 1999-12-07. Retrieved 2022-03-01.
  6. "Pre-boiler and Boiler Corrosion Control | GE Water". Archived from the original on 2017-10-06. Retrieved 2016-03-14.
  7. Merck Index of Chemicals and Drugs, 9th ed. monograph 8451
  8. Larsson, Lars Olof; Kierkegaard, Peder; Lindberg, Bengt; Holme, Tord; Lindberg, Alf A.; Craig, J. Cymerman (1969). "The Crystal Structure of Sodium Sulphite. A Refinement Allowing for the Effect of Crystal Twinning". Acta Chemica Scandinavica. 23: 2253–2260. doi: 10.3891/acta.chem.scand.23-2253 .