sulfite, or calcium sulphite, is a chemical compound which is the calcium salt of sulfurous acid with the molecular formula CaSO₃. 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. Calcium sulfite is a kind of API. There are some basic informations about this crude drug: (1)CAS number: ; (2)PubChem: 159274; (3)ChemSpider: 8329549; (4)Molecular formula: CaSO₃; (5)Molar mass: 120.17 g/mol.