Sulfite is the ion of sulfurous acid, correspondent to tetravalent sulfur. It is used as a conservant in food industry and in beverage production. On the other hand, sulfite is an ecological marker for acid rains occurrence, which may be highly (eco)toxic, reason why its determination is really actual. Being a tetravalent sulfur derivative, sulfite may be either oxidized or reduced. In the case of cathodic reduction, the elemental sulfur or sulfide-ion may be a product, depending on pH.
