Phosphorous acid

Phosphorous acid (CAS 10294-56-1, EC 233-663-1, formula H3PO3) is an inorganic acid also referred to as orthophosphorous acid. It carries no E-code designation and is distinct from phosphoric acid in both oxidation state and reactivity profile.

In water treatment, phosphorous acid functions as a corrosion inhibitor by forming protective complexes on metal surfaces, reducing oxidative degradation in distribution systems. In agriculture, it serves as a bioavailable phosphorus source and antifungal agent, interfering with pathogen cell wall synthesis. It also acts as a reducing antioxidant in chemical synthesis to stabilize sensitive intermediates.

Phosphorous acid is supplied in technical and industrial grades, typically as a solid or concentrated aqueous solution. It falls under REACH regulation (EC 1907/2006) and requires an SDS compliant with EU GHS standards. Packaging formats commonly include drums and IBCs, with quantities available for both laboratory and bulk procurement.