Sulfite (redirected from Sulfites)

sulfite [′səl‚fīt]

(inorganic chemistry)

M₂SO₃A salt of sulfurous acid, for example, sodium sulfite, Na₂SO₃.

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Sulfite 

any of several salts of sulfurous acid, H₂SO₃. Two series of sulfites exist: the normal sulfites, with the general formula M₂SO₃, and the acid sulfites, or hydrogen sulfites, with the general formula MHSO₃, where M is a monovalent metal. Normal sulfites—with the exception of the sulfites of alkali metals and ammonium sulfite—are sparingly soluble in water. They dissolve in the presence of SO₂. Among the acid sulfites, only those of the alkali metals have been isolated in the free state.

Sulfites in aqueous solution are characterized by oxidation to sulfates and reduction to the thiosulfates, M₂S₂O₃. Sulfites are obtained by the reaction of SO₂ with hydroxides or carbonates of the corresponding metals in an aqueous medium. The hydrogen sulfites are more frequently used, and their applications are in the textile industry for dyeing and printing (KHSO₃ and NaHSO₃), in the paper industry for the production of wood pulp [Ca(HSO₃)₂], in photography, and in organic synthesis.