Sodium Sulphite Sodium sulphite is soluble sodium salt of sulfurous acid with chemical formula Na2SO3.Its is used asa preservatives of food and also used as in the same way as sodium Thiosulphate to convert elemental helogens to their hydrohalic acids , in photography and for reducing Chlorine level in pool. Applications Used in pulp and paper industries. Used in water treatment as an oxygen scavenger agent. Used in photography Used in textile industries as a bleaching ,desulfurising and dechlorinating agent. Used in leather industries. Used in the purification of TNT in the military use. Used in chemical industries as sulfonation and sulfomethylation. Used in oil recovery industries. Used in dyes industries.