The system interconverts by oxidation by oxygen and reduction by sodium dithionite. Potassium dithionite (or potassium hydrosulfite) is also an inhibitor of PPO. Dithionite () can also be used as a reductant. The method commercially used by Flexplay and SpectraDisc employs methylene blue reduced by sodium dithionite. Sodium dithionite (), contains the more highly reducing dithionite anion (). Confusion between dithionate and dithionite is commonly encountered, even in manufacturers' catalogues. Reduction of methyl violet occurs in microorganisms but can be attained chemically using sodium dithionite. Thus, solutions of sodium dithionite cannot be stored for a long period of time. Sodium dithionite is produced industrially by reduction of sulfur dioxide. Dithionite is used to bleach wood pulp. Sodium dithionite finds widespread use in industry as a reducing agent. The dithionite is not stable for a long period of time. In aqueous phase nickel or cobalt salts can be reduced, for example, by sodium dithionite. The dithionite anion ([SO]), is an oxoanion of sulfur. Sodium dithionite is a white powder used as a reductant and a bleaching agent.