... pulps, expecially mechanical pupls, it is the most fittable 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 hrdrosulfite food additive grade ... is used in foodstuffs, as bleaching agent andpreservative in dried fruits , dried vegetable ,vermicelli, glucose, sugar, ...