Sodium sulfite is a reducing agent, particularly under basic conditions. Reacts with oxidizing agents such as peroxides, epoxides, oxoacids. Emits toxic fumes of sodium oxide and oxides of sulfur if heated to decomposition [Lewis, 3rd ed., 1993, p. 1174].
As a soluble sodium salt of sulfurous acid, Sodium sulfite (Na2SO3) shows blenching, de-sulfurizing and dechlorinating properties which is widely applied in various fields. It is primarily used in the pulp and papermaking industry due to its blenching activity. It can serve as a good additive to help preserve the fresh appearance of good products. Besides, sodium sulfite is a component in many pharmaceuticals, which is effective to maintain the potency and stability of drugs. It can also be applied for water treatment as an oxygen scavenger agent and applied in flue gas desulfurization and preservation of photo developer solutions, etc.
When ingested, solutions cause gastric irritation by the liberation of sulfurous acid. Because of rapid oxidation to sulfate, sulfites are well tolerated until large doses are reached; then violent colic and diarrhea, circulatory disturbances, central nervous depression, and death can occur.
Sodium sulfite,Na2S03, is a white,water-soluble, crystalline solid with a sulfurous, salty taste. It decomposes when heated. Sodium sulfite is used as a source of sulfite,as a chemical intermediate and food preservative, in medicine and paper manufacturing, in photographic developing, and as a bleaching agent in the textile industry. Most boiler operators use sodium sulfite for chemicals cavenging of oxygen in the feedwater. Because it decomposes into acidic gases at the high temperatures that accompany high pressures, sodium sulfite should not be used for this purpose at pressures above 122atm (12.4MPa,or 1.8 ksi).
Crystallise the sulfite from warm water (0.5mL/g) by cooling to 0o. Also purify it by repeated crystallisation from deoxygenated water inside a glove-box, and finally drying it under vacuum. [Rhee & Dasgupta J Phys Chem 89 1799 1985.]
Literature sources indicate that Sodium sulfite is noncombustible.
Air & Water Reactions
Soluble in water. Reacts with hot water, steam or acids to produce corrosive material.
ChEBI: An inorganic sodium salt having sulfite as the counterion.
Sodium sulfite is mainly used in photographic developers, for fixing prints, bleaching textile fibers, as a reducer in manufacturing dyes, as a remover of Cl in bleached textiles and paper, and as a preservative in the food industry for meat, egg yolks, and so on.
White odorless powder. Density 2.633 g / cm3. Moderately toxic. Sinks in water and dissolves slowly. Also transported as a heptahydrate Na2SO3.7H2O.