Sodium Hydrosulphite (also known as sodium dithionite) is a white crystalline powder with a weak sulfurous odor. Although it is stable under most conditions, it will decompose in hot water and in acid solutions. It can be obtained from sodium bisulfite.

Sodium Hydrosulphite is used as such in some industrial dying processes, where an otherwise water-insoluble dye can be reduced into a water-soluble alkali metal salt. The reduction properties of Sodium Hydrosulphite also eliminate excess dye, residual oxide, and unintended pigments, thereby improving overall colour quality. Reaction with formaldehyde produces Rongalite, which is used as a bleach, in, for instance, paper pulp, cotton, wool, leather, chrome tanning agent and kaolin clay.

Sodium Hydrosulphite can also be used for water treatment, gas purification, cleaning, and stripping. It can also be used in industrial processes as a sulfonating agent or a sodium ion source. In addition to the textile industry, this compound is used in industries concerned with leather, foods, polymers, photography, and many others.