Bleaching action of moist sulphur dioxide is because of its

Solution(By Examveda Team)

In moist conditions, sulphur dioxide is a bleaching agent. In the reducing action of SO₂, oxygen is removed from coloured dye. Sulphur dioxide is used to bleach wool and silk. Salts of sulphur dioxide are also used in bleaching. Calcium hydrogen sulphite Ca(HSO₃)₂ is used to whiten wood pulp in the manufacturing of paper. Other than SO₂, sodium hydrosulphite (Na₂S₂O₄) is also used to bleach wool. However, bleaching using SO₂ is not permanent. On exposure to air and light, the original colour slowly returns as oxygen in air oxidises the bleached substance.