Calcium hydrogen sulphite is an inorganic compound which is the salt of a calcium cation and a bisulfite anion. It may be prepared by reacting lime with an excess of sulfurous acid, essentially a mixture of sulfur dioxide and water.
Potassium hydrogen sulphite is a chemical compound with the chemical formula khso3. It is used during the production of alcoholic beverages as a sterilising agent. This additive is classified as e number E228 under the current eu approved food additive
Sodium hydrogen sulphite is a chemical compound with the chemical formula Nahso3. Sodium bisulfite is a food additive with e number E222. Sodium bisulfite can be prepared by bubbling sulfur dioxide in a solution of sodium carbonate in water. Sodium bisulfite in contact with chlorine bleach (aqueous solution of sodium hypochlorite) will release harmful fumes.