Sodium sulfite



Sodium sulfite
IUPAC name Sodium sulfite
Other names Sodium sulphite
hypo clear (photography)
Identifiers
CAS number 7757-83-7
Properties
Molecular formula Na2SO3
Molar mass 126.0418 g/mol
Appearance white, granular
Density 2.633 g/cm³ (anhydrous)
1.561 g/cm³ (heptahydrate)
Melting point

251.8°C (525 K) (anhydrous)
heptahydrate loses 7H2O at 33.4°C

Boiling point

decomposes

Solubility in water 67.8 g/100 ml of heptahydrate (18°C)
Solubility in other solvents 3 g/100 ml (?°C) (heptahydrate)
Structure
Crystal structure hexagonal (anhydrous)
monoclinic (heptahydrate)
Hazards
Flash point  ?°C
Related Compounds
Related compounds Na2SO4
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Sodium sulfite (sodium sulphite) is a soluble compound of chlorine levels in pools.

Applications

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 (sulfonic acid. It is used to purify or isolate aldehydes and ketones.

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 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.[1]

References

  1. ^ Merck Index of Chemicals and Drugs, 9th ed. monograph 8451
 
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