Sodium dithionite is a whitish to light yellow crystalline solid having a sulfur dioxide-like odor. It spontaneously heats on contact with air and moisture. This heat may be sufficient to ignite surrounding combustible materials. Under prolonged exposure to fire or intense heat containers of this material may violently rupture. It is used in dyeing and to bleach paper pulp. Sodium dithionite is an inorganic sodium salt that is the disodium salt of dithionous acid. It has a role as a reducing agent and a bleaching agent. It contains a dithionite(2-).

It is widely used for reductive dyeing, reduction cleaning, printing and decolorization in the textile industry, as well as for bleaching fabrics such as silk, wool and nylon. Since it contains no heavy metals, the bleached fabrics have bright colors and are not prone to fading.

It can also be used for food bleaching, including gelatin, sucrose, preserves, as well as bleaching soap, animal (vegetable) oils, bamboo products and porcelain clay.

It can be applied in organic synthesis, such as being used as a reducing agent or bleaching agent in the production of dyes and pharmaceuticals. Sodium dithionite is the most suitable bleaching agent for wood pulp papermaking.