Sodium sulfite
From Wikipedia, the free encyclopedia
| Sodium sulfite | |
|---|---|
 |
|
| IUPAC name |
|
| Other names | Hypo clear (photography) E221 |
| Identifiers | |
| CAS number | [] |
| PubChem | |
| RTECS number | WE2150000 |
| Properties | |
| Molecular formula | Na2SO3 |
| Molar mass | 126.043 g/mol |
| Appearance | white solid |
| Density | 2.633 g/cm3 (anhydrous) 1.561 g/cm3 (heptahydrate) |
| Melting point |
33.4 °C (dehydration of heptahydrate) |
| Boiling point |
Decomposes |
| Solubility in water | 67.8 g/100 ml (18 °C, heptahydrate) |
| Structure | |
| Crystal structure | hexagonal (anhydrous) monoclinic (heptahydrate) |
| Hazards | |
| MSDS | ICSC 1200 |
| EU Index | Not listed |
| NFPA 704 |
 0
2
0
|
| Flash point | Non-flammable |
| Related compounds | |
| Other anions | Sodium selenite |
| Other cations | Potassium sulfite |
| Related compounds | Sodium bisulfite Sodium metabisulfite Sodium sulfate |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
|
Sodium sulfite (sodium sulphite) is a soluble compound of sodium. 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.
Contents |
[edit] 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 (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 ore flotation, oil recovery, food preservatives, making dyes, and detergent.
[edit] 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.
[edit] 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.[1]
[edit] Hazards
Parenteral injection containing sodium sulfite may cause life-threatening allergic reactions.[citation needed]
[edit] References
- ^ Merck Index of Chemicals and Drugs, 9th ed. monograph 8451
|
|||||
