Calcium bisulfite

Calcium bisulfite (CAS 13780-03-5) is an inorganic sulfite salt, also referred to as calcium hydrogensulfite or calcium bisulphite. It is distinct from calcium metabisulfite and is supplied as an aqueous solution rather than a dry powder. No E-number designation applies to this compound under current EU food additive legislation.

In water treatment, calcium bisulfite acts as a reducing agent to scavenge residual chlorine from process streams, neutralising oxidative damage to downstream membranes and resins. In pulp and paper production, it delignifies wood chips by breaking sulfonate bonds within lignin under acidic conditions, enabling cellulose separation without excessive fibre degradation.

Calcium bisulfite is typically supplied as a stabilised aqueous solution and must comply with REACH registration requirements for industrial supply within the EU. Buyers should confirm solution concentration and purity grade against their process specification. Packaging formats commonly include IBC containers and bulk tanker delivery for high-volume industrial users.