What does bisulphite mean?
Bisulphite is a noun referring to any salt or ester derived from bisulphurous acid, characterised chemically by the presence of the HSO₃⁻ (hydrogen sulphite) anion. The most familiar examples are sodium bisulphite and calcium bisulphite, both valued industrially for their properties as reducing agents and oxygen scavengers. In everyday life, bisulphites are encountered most often as food preservatives — particularly in dried fruits, fruit juices, and wine, where they inhibit microbial growth and prevent browning by blocking oxidation. They also have long-standing roles in photography, paper pulping, and water treatment. The word is essentially technical in register, appearing in scientific literature, ingredient labels, and industrial documentation rather than casual conversation. Spelled with '-ph-' in British English but with '-f-' ('bisulfite') in American English, it belongs to the broader family of sulphur-derived chemical names such as sulphate, sulphide, and sulphite. Its practical importance lies less in its linguistic elegance than in its quiet ubiquity across food, industry, and laboratory practice worldwide.
nounA salt or ester of bisulphurous acid, containing the anion HSO₃⁻; in chemistry, a compound formed from sulphur dioxide and a base, widely used as a preservative and reducing agent.
- In chemistry, a salt of bisulphurous acid containing the HSO₃⁻ anion.
- An ester derived from bisulphurous acid.
"The winemaker added a small quantity of sodium bisulphite to prevent the wine from oxidising."
"Photographers once used sodium bisulphite to fix images on film, exploiting its reducing properties."
"Calcium bisulphite was historically used in papermaking to dissolve lignin during the pulping process."
The plural is standard and typically appears when discussing several distinct compounds or when referring generically to a class of preservatives, as on food labels.
"Some people are sensitive to bisulphites, which must be declared on packaged food labels above certain concentrations."
That sharp tang of dried fruit and white wine? Often thanks to bisulphites — the same compounds that have been preserving food since Roman times.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bisulphite
Bisulphite derives from the Latin noun 'sulphur' (also spelled 'sulpur'), meaning brimstone, which entered English via Old French as 'sulphre' before settling into modern forms. The prefix 'bi-' here indicates the addition of one hydrogen atom relative to ordinary sulphite, reflecting nineteenth-century chemical naming conventions rather than literal doubling. It is closely cognate with other sulphur-based terms such as sulphate, sulphide, and sulphite, all coined within the systematic nomenclature developed by European chemists in the late eighteenth and early nineteenth centuries. The American variant spelling 'bisulfite' reflects Noah Webster's later reforms that simplified '-ph-' to '-f-' in certain words.
Related word forms
How bisulphite is actually used
Bisulphite is chiefly a technical term used in chemistry, food science, and industry; it is rarely heard outside these domains. The spelling 'bisulphite' follows British conventions using '-ph-'; American usage prefers 'bisulfite' with '-f-'. In food-labelling contexts the related plural form 'bisulphites' is common when referring collectively to such preservatives.
Easily confused with bisulphite
Sulphite refers to salts containing the divalent SO₃²⁻ anion, whereas bisulphite (or hydrogensulphite) specifically denotes salts containing the monovalent hydrogen-bearing HSO₃⁻ anion.