British variant spelling of bisulfite; a chemical salt used as a food preservative and in industrial processes.
From bi- + sulphite (British spelling of sulfite, using 'ph'). Standard British chemical nomenclature from the 19th century onward.
Wine bottles worldwide say 'contains sulphites' because British English got there first—British winemakers and chemists exported their terminology along with their products, making spelling choices into global standards.
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