EC No 231-821-4 SSA Sodium Sulfite for Water Treatment Oxygen Scavenger Agent

ANHYDROUS SODIUM SULFITE/SODIUM SULPHITE               FOR WATER TREATMENT 

Sodium sulfite
Other names
Hypo clear(photography)
E221
Identifiers
CAS Number · 7757-83-7
3D model (JSmol) · Interactive image
ChEBI · CHEBI:86477
ChemSpider · 22845
ECHA InfoCard 100.028.929
EC Number 231-821-4
E number E221 (preservatives)
PubChem CID · 24437
RTECS number WE2150000
UNII · VTK01UQK3G
InChI[show]
SMILES[show]
Properties
Chemical formula Na2SO3
Molar mass 126.043 g/mol
Appearance white solid
Odor odorless
Density 2.633 g/cm3 (anhydrous)
1.561 g/cm3 (heptahydrate)
Melting point 33.4 °C (92.1 °F; 306.5 K) (dehydration of heptahydrate)
500 °C (anhydrous)
Boiling point Decomposes(separate (substances) into constituent elements)
Solubility in water 27.0 g/100 mL water (20 °C)
Solubility soluble in glycerol insoluble in ammonia,chlorine
log P -4
Acidity (pKa) ~9 (heptahydrate)
Refractive index(nD) 1.565
Structure
Crystal structure hexagonal (anhydrous)
monoclinic (heptahydrate)
Hazards
Safety data sheet ICSC 1200

Applications

Sodium sulfite is primarily used in the pulp and paper industry. It is used in water treatment as an oxygen scavenger agent, to treat water being fed to steam boilers to avoid corrosion problems,[2] 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 the purification of TNT for military use. 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 froth flotation of ores, oil recovery, food preservatives, and making dyes.

SODIUM SULFITE is a white odorless powder. Density 2.633 g / cm3. Moderately toxic. Sinks in water and dissolves slowly. Also transported as a heptahydrate Na2SO3.7H2O.

Reactions

Sodium sulfite forms a bisulfite adduct with aldehydes, and with ketones forms a sulfonic acid. It is used to purify or isolate aldehydes and ketones.

Sodium sulfite (sodium sulphite) is a soluble sodium salt of sulfurous acid (sulfite) with the chemical formula Na2SO3. It is a product of sulfur dioxide 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 halogens to their respective hydrohalic acids, in photographyand for reducing chlorine levels in pools.
Sodium Sulfite is a white crystal or powder with reducing property. Sodium sulfite exhibits bleaching, de-sulfurizing, and dechlorinating activities. This agent was used by food industry to help maintain the fresh appearance of food products. It is also a component in many drugs, which helps maintain their potency and stability. FDA has ruled sodium sulfite a new animal drug of low regulatory priority.

Descriptive chemistry

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.