Although sulfurous acid is not an important compound, many sulfites are widely used. Sulfites react
with sulfur to produce thiosulfates (see Eq. (15.5)), and sulfites are reducing agents that are used in
large quantities, particularly in the sulfite process for making paper pulp. Sulfites are oxidized to sulfates by oxidizing agents such as MnO 4
, Cl 2, I 2, and Fe 3 . Most bisulfite salts are those in which the
cation is a 1 ion of large size.