Calcium sulfite
Calcium sulfite, or calcium sulphite, is a chemical compound which is the calcium salt of sulfurous acid with the molecular formula CaSO3. Some common uses areits production in flue gas desulfurization (FGD), as a food additive, and in the production of calcium sulfate. It commonly reacts to create calcium sulfite hemihydrate when in the presence of moist air.
Uses
Wood Pulp Production
Calcium sulfite can be used in the production of wood pulp through the Kraft Process. Chemical wood pulping is the removal of cellulose from wood by dissolving the lignin that binds the cellulose together. Calcium sulfite was used, but has been largely replaced by magnesium and sodium sulfites and bisulfites to attack the lignin[].
Food Additive
As a food additive it is used as a preservative under the E number E226. It is commonly used in preserving wine, cider, fruit juice, canned fruit and vegetables. Sulfites are strong reducers, as sulfate formation is favored so they act as somewhat of an O2 scavenger to preserve food.