Sulfur dioxide

Sulfur dioxide (SO2, also known as R-764 or sulphur dioxide) is an inorganic gas produced primarily by the combustion of sulfur-containing compounds. It carries no E-code designation for direct food use in this form, though it serves as the active species behind several approved food additives in the sulfite family.

In water treatment, SO2 reduces residual chlorine through direct chemical reaction, converting hypochlorous acid to hydrochloric acid and sulfate. In pulp and paper, it bleaches mechanical pulp by reducing chromophoric lignin structures. Mining operations use it in the INCO process to detoxify cyanide-bearing tailings, oxidising free cyanide under alkaline conditions.

Sulfur dioxide is supplied as a liquefied compressed gas in cylinders and ISO tanks, suitable for industrial and food-grade applications. Procurement should confirm compliance with REACH registration requirements and, where food contact is intended, verify FCC or equivalent purity specifications with the supplier prior to ordering.