Sodium Hydrosulfite (Na2S2O4) is a free flowing, dry, white uniformly crystalline powder. In aqueous solution, it exhibits strong reducing properties toward most metal salts and many organic compounds.

Sodium hydrosulfite is very stable when stored in dry, closed containers. It spontaneously decomposes when heated above 75-80ÂșC. When a 1-% solution is prepared in oxygen-free water, the pH value is approximately 8. Below a pH of 5 decomposition is rapid. The solution stability may be improved by adding a buffering agent to maintain a slightly alkaline solution. If the moisture level reaches 15%, or the material is exposed to moist air, rapid decomposition can occur, with development of heat and potential fire hazard.

CAS: 7775-14-6

Molecular Weight: 174.1

STORAGE: Sodium hydrosulfite by nature is a very reactive chemical which can decompose when
exposed to air and moisture, with the evolution of sufficient heat to spontaneously ignite to fire. It must
be stored in a sealed, dry, clean container in a cool and dry place, away from acids, oxidizing agents
and combustible organic substances. It must be kept away from moisture, water and heat. It should be
handled and stored with care.


Hydrosulfite is used extensively in the textile industry for vat dyeing, reducing cleaning, printing and

Sodium hydrosulfite is also used as a bleaching agent for textile materials, such as silk, wool, and
nylon, etc.

It can be used to bleach foodstuffs such as gelatin, sugar, honey, wine and vegetables, etc.

It is also used for bleaching miscellaneous substances, such as soaps, oils, fats, and china clay.

The preparation of dyestuffs and pharmaceuticals uses Sodium Hydrosulfite as reducing or
bleaching agent.

Sodium hydrosulfite is used for bleaching woodpulp where it can be most economical to produce
gains of up to 10 points in brightness under controlled conditions, such as temperature, pH value
and retention time.