... pulps, especially mechanical pulps; its the most fitable bleaching agent in pulps. 3. It is used in bleaching kaolin ... thiourea and other sulphides. 5. It is used as reducing agent in chemical industry.6. Sodium hydrosulfite food additive grade is ... used in foodstuffs, as bleaching agent and preservative dried fruits, dried vegetable, vermicelli, glucose, sugar, ...