Sulfite

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A space-filling model of the sulphite anion.

Sulfites (also sulphite) are compounds that contain the sulfite ion S O₃²⁻. They are often used as preservatives in wines (to prevent spoilage and oxidation), dried fruits, and dried potato products. Sulfites also occur naturally in almost all wines.

1 Chemical properties
- 1.1 Related sulfur oxoanions
2 Health risks
- 2.1 Regulation of commercial use
3 See also
4 External links

[edit] Chemical properties

The structure of the sulfite anion

S O₃²⁻ is a polyatomic ion, in which two or more atoms are bonded together to form a charged species, which most often is treated as, in effect, a charged molecule. S O₃²⁻ is also an oxoanion, which refers to a polyatomic ion which contains one or more oxygen atoms. The Sulfite ion contains one oxygen double bond, other two oxygen have single bonds and one lone pair of electrons. According to the VSEPR model, it is classified as trigonal pyramid.

[edit] Related sulfur oxoanions

S O₅²⁻ persulfate ion
S O₄²⁻ sulfate ion
S O₃²⁻ sulfite ion
S O₂²⁻ hyposulfite

[edit] Health risks

Some animals are allergic to sulfites, and may have difficulty breathing within minutes of eating a food containing sulfites. Asthmatics and people with allergies to aspirin are at an elevated risk for reaction to sulfites. The reaction can be fatal and requires immediate treatment at an emergency room, and can include sneezing, swelling of the throat, and hives. Those who are allergic to sulfites are urged to avoid products that could contain them.

See also: anaphylaxis

[edit] Regulation of commercial use

Sulfites occur naturally in wine. They are also added to wine. In the US, wine bottled after mid-1987 must have a label stating that they contain sulfites if they contain more than 10 parts per million. In the EU an equivalent regulation came into force in November 2005 [1]. Organic wines are not necessarily sulfite-free but they have no added sulfites. Most beers no longer contain sulfites. Although shrimp is sometimes treated with sulfites on fishing vessels, the chemical may not appear on the label. In 1985, the United States federal government banned the addition of sulfites to most fresh fruits and vegetables, though fresh-cut potatoes and dried fruits are exceptions.