Sodium sulfite
From Wikipedia, the free encyclopedia
Sodium sulfite | ||
---|---|---|
Image:Sodium sulfite.jpg | ||
General | ||
Systematic name | Sodium sulfite | |
Other names | hypo clear (photography) | |
Molecular formula | Na2SO3 | |
SMILES | ? | |
Molar mass | 126.0418 g/mol | |
Appearance | white, granular | |
CAS number | [?-?-?] | |
Properties | ||
Density and phase | 2.633 g/cm³ (anhydrous) 1.561 g/cm³ (heptahydrate) |
|
Solubility in water | 67.8 g/100 ml of heptahydrate (18°C) | |
Solubility in glycerol | 3 g/100 ml (?°C) (heptahydrate) | |
Melting point | 251.8°C (525 K) (anhydrous) heptahydrate loses 7H2O at 33.4°C |
|
Boiling point | decomposes | |
Structure | ||
Molecular shape | ? | |
Coordination geometry |
? | |
Crystal structure | hexagonal (anhydrous) monoclinic (heptahydrate) |
|
Dipole moment | ? D | |
Hazards | ||
MSDS | External MSDS | |
Main hazards | ? | |
NFPA 704 | ||
Flash point | ?°C | |
R/S statement | R: ? S: ? |
|
RTECS number | ? | |
Supplementary data page | ||
Structure and properties |
n, εr, etc. | |
Thermodynamic data |
Phase behaviour Solid, liquid, gas |
|
Spectral data | UV, IR, NMR, MS | |
Related compounds | ||
Other anions | ? | |
Other cations | ? | |
Related ? | ? | |
Related compounds | SO2 H2SO3 Na2SO4 |
? |
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references |
In chemistry, sodium sulfite 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 desulfurisation 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.
Contents |
[edit] Applications
It 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 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 used in other applications, include 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.
[edit] Descriptive Chemistry
Sodium sulfite is decomposed by even weak acids, giving up sulfur dioxide gas.
- Na2SO3 + 2H+ → 2Na+ + 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 crystalize 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[1].
[edit] References
- ^ Merck Index of Chemicals and Drugs, 9th ed. monograph 8451