Project Report on Anhydrous Sodium Dithionite Production

Sodium Hydrosulfite, also known as Sodium Dithionite had been developed at the beginning of the 20th century and was first applied for textile printing. Due to structural change in the textile industry, the importance of the  application for the bleaching of wood pulp in the paper industry increased continuously. Sodium Hydrosulfite is a white powder. Commercial sodium hydrosulfite contains 85% - 90% sodium dithionite w/w. It is readily soluble in water and shows powerful reducing action in aqueous solutions. Sodium hydrosulfite is used as a reducing agent in dying application. It undergoes reduction reaction  with water-insoluble vat dye and sulfur dye to form water-soluble alkali metal salt of the dye (leuco form ) so that they have affinity  for the textile fiber. The reductive  decomposition of the excessive dye by sodium hydrosulfite improve the colour fastness.  Sodium hydrosulfite's  reduction  reaction removes residual oxide and  wrong pigments. Sodium  hydrosulfite  is a reductive  bleaching  agent.  It  reduces carbonyl and  alcohol groups, which function as colorants of the substances. It is used in  bleaching mechanical paper pulp, cotton, and wool and  kaolin clay.