Sodium sulfite(sodium sulphite) is a soluble compound of sodium. Its chemical formula is Na2SO3. It has a molecular weight of 126.04. It is a product of SO2 scrubbing, a part of the flue gas desulfurization process. It is also used as a preservative to prevent dried fruit from discoloring, and for preserving meats, and is used in the same way as sodium thiosulfate to convert elemental halides to their respective acids, in photography and for reducing chlorine levels in pools.
Sulfites are salts or esters of sulfurous acid (H2SO3), formed by replacing one or both of the hydrogens with a metal or a radical as in sodium sulfite, Na2SO3. Sulfites in which both hydrogens are replaced are called normal sulfites. Bisulfite is a compound that has the HSO3- radical. Bisulfate (called also hydrogen sulfite or acid sulfite) is a compound formed by replacing only one hydrogen in sulfurous acid. The term of ‘meta’ or ‘pyro’ is the chemical prefix for oxo acid formed through the loss of one water molecule (dehydration) from two molecules of ortho acid by heating.
Sodium sulfite is decomposed by even weak acids, giving up sulfur dioxide gas.
Na2SO3 + 2 H+ → 2 Na+ + H2O + SO2
A saturated aqueous solution has pH of ~9. Solutions exposed to air are eventually oxidized to sodium sulfate. If sodium sulfite is allowed to crystallize from aqueous solution at room temperature or below, it does so as a heptahydrate. The heptahydrate crystals effloresce in warm dry air. Heptahydrate crystals also oxidize in air to form the sulfate. The anhydrous form is much more stable against oxidation by air
Sodium sulfite is primarily used in the pulp and paper industry. It is used in water treatment as an oxygen scavenger agent, in the photographic industry to protect developer solutions from oxidation and (as hypo clear solution) to wash fixer (sodium thiosulfate) from film and photo-paper emulsions, in the textile industry as a bleaching, desulfurizing and dechlorinating agent and in the leather trade for the sulfitization of tanning extracts. It is used in chemical manufacturing as a sulfonation and sulfomethylation agent.
It is used in the production of sodium thiosulfate. It is used in other applications, including ore flotation, oil recovery, food preservatives, making dyes, and detergent. It forms a bisulfite adduct with aldehydes, and with ketones forms a sulfonic acid. It is used to purify or isolate aldehydes and ketones.
It is used in water treatment as an oxygen scavenger agent , in the photographic industry to protect developer solutions from oxidation, in textile industry as a bleaching, as a desulfurizing and as a dechlorinating agent and in leather trade for the sulfitization of tanning extracts. It is used in chemical manufacturing as a sulfonation and sulfomethylation agent. It is used in the production of sodium thiosulfate.
It is use in other applications include ore flotation, oil recovery, food preservative, making dyes, and detergent. It forms a bisulfite adduct with aldehyde and with ketones to a sulfonic acid. It is used to purify or isolate aldehydes and ketones.
|TOXICITY||Oral mouse LD50: 820 mg/kg|
Sodium sulfite anhydrous; disodium sulfite; Natrii Sulphis; Natrium Sulfurosum; Natriumsulfit (German); sulfurous acid, disodium salt;
|PHYSICAL AND CHEMICAL PROPERTIES|
|PHYSICAL STATE||White crystalline powder|
|SOLUBILITY IN WATER||good|
|NFPA RATINGS||Health: 1 Flammability: 0 Reactivity: 0|
|STABILITY||Stable under ordinary conditions|
|APPEARANCE||White crystalline powder|
|HEAVY METALS||10ppm max|
|pH||9.5 – 10.5|