sulfity

Sulfity is a nonstandard or historical term that is sometimes used to refer to sulfite, the sulfite ion SO3^2− and its salts. In modern chemistry, sulfite is the preferred term, and bisulfite (HSO3−) is used for the protonated form that occurs at different pH. The use of sulfity in English-language chemistry is uncommon and may appear in older literature or as a translation artifact.

Chemistry and properties

Sulfite arises from sulfurous acid (H2SO3) and exists in aqueous solution as a base that equilibrates with bisulfite depending on the pH. In acidic conditions, sulfite can be converted to sulfurous acid and release sulfur dioxide (SO2) gas. Sulfite ions readily act as reducing agents in some reactions and can be oxidized to sulfate (SO4^2−) under appropriate conditions. Sulfites form salts with alkali and alkaline earth metals, such as sodium sulfite (Na2SO3) and potassium sulfite (K2SO3), as well as bisulfite salts like sodium bisulfite (NaHSO3).

Uses

Sulfite salts are used in several industrial and commercial applications. In food and beverage processing, sulfites serve as antioxidants and preservatives, helping to prevent browning and spoilage; they are commonly found in wines, dried fruits, and certain processed foods. The pulp and paper industry historically employed sulfite pulping. Sulfites also appear in photography and in some water-treatment and chemical-reducing applications.

Health and safety

Some individuals exhibit sulfite sensitivity, particularly those with asthma, and exposure can provoke adverse reactions in susceptible people. In acidic environments, sulfites release SO2, a toxic gas with irritant properties. Many jurisdictions require labeling of sulfite-containing foods and beverages when levels exceed regulatory thresholds, which are commonly around 10 mg/kg.