Sodium metabisulfite explained

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.

Preparation

See also: Wellman–Lord process. Sodium metabisulfite can be prepared by treating a solution of sodium hydroxide with sulfur dioxide.[1] When conducted in warm water, Na2SO3 initially precipitates as a yellow solid. With more SO2, the solid dissolves to give the disulfite, which crystallises upon cooling.[2]

SO2 + 2 NaOH → Na2SO3 + H2O

SO2 + Na2SO3 → Na2S2O5which yields a residue of colourless solid Na2S2O5.

Chemical structure

The anion metabisulfite consists of an SO2 group linked to an SO3 group, with the negative charge more localised on the SO3 end. The S–S bond length is 2.22 Å, and the "thionate" and "thionite" S–O distances are 1.46 and 1.50 Å, respectively.[3]

Reactivity

Upon dissolution in water, bisulfite is generated:

Na2S2O5 + H2O → 2 Na+ + 2 HSO3

Uses

Sodium and potassium metabisulfite have many major and niche uses. It is widely used for preserving food and beverages.

Safety

Sodium metabisulfite, despite not being flammable, decomposes in 150 °C of heat releasing toxic gasses when decomposed. It is corrosive when dissolved in water.

External links

Notes and References

  1. Book: Inorganic Chemistry, 3rd Edition. Chapter 16: The group 16 elements. Catherine E. Housecroft. Alan G. Sharpe. Pearson. 2008. 978-0-13-175553-6. 520.
  2. Book: 10.1002/9780470132333.ch49. 9780470132333. Sulfites and Pyrosulfites of the Alkali Metals. 1946. Johnstone. H. F.. Inorganic Syntheses. 162–167. 2.
  3. K. L. Carter, T. A. Siddiquee, K. L. Murphy, D. W. Bennett "The surprisingly elusive crystal structure of sodium metabisulfite" Acta Crystallogr. (2004). B60, 155–162.
  4. Book: McGee . Douglas L. . Roberts . James R. . Jerris . R. Hedges . Roberts and Hedges' Clinical Procedures in Emergency Medicine . 2013 . Elsevier/Saunders . 9781455748594 . 519 . 6th . https://books.google.com/books?id=slyLreFkHuIC&pg=PA519 . Local and topical anesthesia.
  5. Book: Niazi . Safaraz K. . Handbook of Pharmaceutical Manufacturing Formulations. Volume 6, Sterile Products . 2009 . Informa Healthcare . New York . 9781420081312 . 410 . 2nd .
  6. Book: Barnes, Andrew R. . Chapter 48. Chemical stability in dosage forms. Aulton . Michael E. . Taylor . Kevin M.G. . Aulton's pharmaceutics : the design and manufacture of medicines . 2013 . Churchill Livingstone/Elsevier . 9780702053931 . 833 . 4th . https://books.google.com/books?id=SZ43AAAAQBAJ&pg=PA833.
  7. Web site: Ingredients . Summit Brands . 31 October 2019 . 25 April 2021.
  8. Book: Anchell. Steve. The darkroom cookbook. limited. 2008. Focal Press. Amsterdam. 978-0240810553. 193. 3rd.
  9. http://www.bonideproducts.com/lbonide/msds/sds271.pdf
  10. Web site: Color Metallography. 2011-05-04.
  11. Web site: ETCHING ISOTHERMALLY TREATED STEELS. PDF. George F. Vander Voort. Asminternational.org. 24 January 2022. 16 October 2022. https://web.archive.org/web/20221016054106/https://www.asminternational.org/documents/10192/1874035/htp00102p025.pdf/ace8f01d-bf9a-4048-b948-a3aeb2d8a536. dead.
  12. Web site: Micro-Pak Enhanced Packaging Stickers. 2020-05-05.
  13. Book: https://www.sciencedirect.com/science/article/pii/B9781845697358500152 . Postharvest Biology and Technology of Tropical and Subtropical Fruits. 15 - Litchi (Litchi chinensis Sonn.). Woodhead Publishing Series in Food Science, Technology and Nutrition. 10.1533/9780857092885.361 . 2020-05-05. 361–409e. Woodhead. 9781845697358. Sivakumar. D.. Korsten. L..
  14. Manek. Rahul V.. Builders. Philip F.. Kolling. William M.. Emeje. Martins. Kunle. Olobayo O.. June 2012. Physicochemical and binder properties of starch obtained from Cyperus esculentus. AAPS PharmSciTech. 13. 2. 379–388. 10.1208/s12249-012-9761-z. 1530-9932. 3364391. 22350737.
  15. Nawab. Anjum. Alam. Feroz. Haq. Muhammad Abdul. Hasnain. Abid. 2016. Biodegradable film from mango kernel starch: Effect of plasticizers on physical, barrier, and mechanical properties. Starch - Stärke. en. 68. 9–10. 919–928. 10.1002/star.201500349. 1521-379X.
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  17. Park. S. H.. Bean. S. R.. Wilson. J. D.. Schober. T. J.. 2006. Rapid Isolation of Sorghum and Other Cereal Starches Using Sonication. Cereal Chemistry. en. 83. 6. 611–616. 10.1094/CC-83-0611. 1943-3638.