sulfite

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sulfite

chemical compound

Also known as: sulphite

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Last updated

July 14, 2026

Quick Summary

A sulfite is a salt of sulfurous acid, containing the sulfite ion (SO₃^2-). Sulfites are formed when sulfur dioxide dissolves in water, creating a solution that acts as a moderately strong acid. This process yields sulfites and hydrogen sulfites (HSO₃^-).1

Key facts about sulfites:
* Uses: Sulfites are used as reducing agents, bleaching agents, and in food preservation, particularly for fruits and vegetables. They are also used in wine making and the paper-pulp industry.12
* Properties: Most sulfite salts are relatively insoluble, except for alkali metal sulfites. Sulfites and hydrogen sulfites are moderately strong reducing agents and can be oxidized to sulfates.1
* Forms: Sodium sulfite (Na₂SO₃) is a common example, used as a reducing agent, bleaching agent, and in photographic processes.3

Sulfur itself is a nonmetallic element, pale yellow in colour, and insoluble in water. It forms various compounds, including sulfides, sulfites, and sulfates, with oxidation states of -2, +4, and +6.4

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oxyacid
Sulfurous acid and sulfite salts
When sulfur dioxide is dissolved in water, an acidic solution results. This has long been loosely called a sulfurous acid, H₂SO₃, solution. However, pure anhydrous sulfurous acid has never been isolated or detected, and an aqueous solution of SO₂ contains little, if any,…
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When sulfur dioxide is dissolved in water, an acidic solution results. This has long been loosely called a sulfurous acid, H₂SO₃, solution. However, pure anhydrous sulfurous acid has never been isolated or detected, and an aqueous solution of SO₂ contains little, if any,…
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food additive
Antimicrobials
Sulfur dioxide and sulfites are used to control the growth of spoilage microorganisms in dried fruits, fruit juices, and wines. Nisin and natamycin are preservatives produced by microorganisms. Nisin inhibits the growth of some bacteria, while natamycin is active against molds and yeasts.
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Sulfur dioxide and sulfites are used to control the growth of spoilage microorganisms in dried fruits, fruit juices, and wines. Nisin and natamycin are preservatives produced by microorganisms. Nisin inhibits the growth of some bacteria, while natamycin is active against molds and yeasts.
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vegetable processing
Dehydration
A small amount of sulfite may be used in producing certain dried vegetables. The sulfite serves as an antimicrobial agent, aids in heat transfer, and (in the case of potatoes) acts as a blanching agent. A small percentage of the consumer population is allergic to sulfite. Although the rehydrated…
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A small amount of sulfite may be used in producing certain dried vegetables. The sulfite serves as an antimicrobial agent, aids in heat transfer, and (in the case of potatoes) acts as a blanching agent. A small percentage of the consumer population is allergic to sulfite. Although the rehydrated…
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food preservation
Inorganic chemical preservatives
Sulfur dioxide and sulfites are perhaps the most important inorganic chemical preservatives. Sulfites are more effective against molds than against yeasts and are widely used in the preservation of fruits and vegetables. Sulfur compounds are extensively used in wine making and, as in most other instances when this…
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Sulfur dioxide and sulfites are perhaps the most important inorganic chemical preservatives. Sulfites are more effective against molds than against yeasts and are widely used in the preservation of fruits and vegetables. Sulfur compounds are extensively used in wine making and, as in most other instances when this…
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chemical compound
Ionic compounds containing polyatomic ions
For example, SO₃²⁻ is called sulfite and SO₄²⁻ is called sulfate. In those cases where more than two oxy anions constitute the series, hypo- (less than) and per- (more than) are used as prefixes to name the members of the series with the smallest and the largest number of oxygen…
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For example, SO₃²⁻ is called sulfite and SO₄²⁻ is called sulfate. In those cases where more than two oxy anions constitute the series, hypo- (less than) and per- (more than) are used as prefixes to name the members of the series with the smallest and the largest number of oxygen…
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