Potassium bisulfite

Potassium bisulfite (CAS 7773-03-7), also known as potassium hydrogen sulfite or potassium acid sulfite, is an inorganic potassium salt that releases sulfur dioxide in solution. It is not assigned an E-number and should not be confused with potassium metabisulfite (E224), a related but distinct compound.

In water treatment, potassium bisulfite acts as a reducing agent to neutralise residual chlorine in process streams, preventing oxidative damage to downstream membranes and ion-exchange resins. In textile and paper processing, it functions as a bleaching and reducing agent, breaking chromophoric bonds to lighten fibres and pulp without the harshness of chlorine-based alternatives.

Potassium bisulfite is supplied as a white crystalline powder in technical and food-contact grades, with compliance documentation available for REACH registration requirements. Standard packaging includes 25 kg bags. Buyers should confirm grade suitability against applicable specifications such as FCC for food-adjacent applications.