What does sulfite mean?
A sulfite is a chemical compound containing the negatively charged sulfite ion, SO₃²⁻, generally formed by combining this ion with a metal such as sodium or potassium. Sulfites are used in various industrial processes and also occur in wine and many dried foods because sulfur-dioxide-related compounds slow microbial spoilage and preserve color and flavor. The term is especially familiar from food labels: products made with sulfites must declare them, and a small number of people—particularly some people with asthma—experience serious allergic-type reactions after consuming them. In chemistry, a sulfite should not be confused with a sulfate, whose ion contains an additional oxygen atom. The word is related etymologically to sulfur and the adjective sulfurous, and it also has the conventional British spelling “sulphite.”
nounA sulfite is a chemical compound containing the sulfite ion, SO₃²⁻, usually as the salt of a metal such as sodium or potassium. The term also refers to sulfur dioxide or related sulfite compounds used to preserve foods and wines.
- A salt or other compound containing the sulfite ion, SO₃²⁻.
- Sulfur dioxide or related sulfite compounds used as food preservatives, especially in wine and dried foods.
"The manufacturer listed sodium sulfite among the ingredients used to prevent spoilage."
"Sodium sulfite is used in some industrial processes and food-preservation applications."
"The wine contains naturally occurring sulfites, as indicated on its label."
The plural is standard in chemical contexts and in the common food-allergy notice “contains sulfites.”
"Products that contain sulfites must display the relevant allergen declaration."
Sulfites are useful preservatives, but their labels on wine and dried fruit can also trigger severe reactions in some people with asthma.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sulfite come from?
The word was formed in the 19th century from “sulfur,” also spelled “sulphur,” and the chemical suffix “-ite,” which commonly names salts of particular acids. Its terminology reflects sulfur’s ancient association with several mineral acids and their salts. The related words sulfur, sulfuric, and sulfurous all share the same lexical root.
Related word forms
How sulfite is actually used
In food labeling, “contains sulfites” is a standard warning because sulfites can provoke serious reactions, particularly in people with asthma, though the sensitivity is uncommon.
Easily confused with sulfite
A sulfite contains the ion SO₃²⁻, whereas a sulfate contains SO₄²⁻ and has one more oxygen atom.
A sulfide contains sulfur with an oxidation state of −2, while a sulfite contains the polyatomic ion SO₃²⁻.