Sodium sulfite
Structural formula | ||||||||||||||||
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General | ||||||||||||||||
Surname | Sodium sulfite | |||||||||||||||
other names |
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Molecular formula | Na 2 SO 3 | |||||||||||||||
Brief description |
white, crystalline, odorless powder |
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properties | ||||||||||||||||
Molar mass | 126.04 g mol −1 | |||||||||||||||
Physical state |
firmly |
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density |
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Melting point |
Decomposition from 500 ° C |
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solubility |
Easily soluble in water (220 g l −1 at 20 ° C) |
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safety instructions | ||||||||||||||||
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Toxicological data | ||||||||||||||||
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Sodium sulfite Na 2 SO 3 (not to be confused with sodium sulfide Na 2 S) is the sodium salt of sulphurous acid .
Extraction and presentation
Sodium sulphite is formed when sulfur dioxide is introduced into sodium hydroxide solution
or by neutralizing caustic soda with sulphurous acid.
Sodium sulfite can also be obtained by reacting a sodium hydrogen sulfite solution with sodium hydroxide solution or a sodium carbonate solution and is also formed as a by-product in the production of naphthols and / or phenols from naphthalene and benzenesulfonic acids .
properties
Sodium sulfite is a white to slightly yellowish, odorless, crystalline powder. It crystallizes out as a heptahydrate from aqueous solution . It is hygroscopic and can be prepared by oxygen to sodium sulfate (Na 2 SO 4 ) is oxidized to be. With acids it decomposes with the formation of sulfur dioxide. The heptahydrate splits off water of crystallization from 150 ° C. The water-free form is more stable to oxidation than the heptahydrate. Sodium sulfite is easily soluble in water, the solution has an alkaline reaction and has a reducing effect (for example, potassium permanganate solution is discolored). It has a germicidal effect.
The compound has a trigonal crystal structure with the space group P 3 (space group no. 147) .
use
- Sodium sulfite serves as a preservative and antioxidant for food (additive number E221). As part of the so-called dumpling aid , it prevents potato dough from turning brown (oxidizing). In the photo industry , sodium sulfite anhydrous photo grade is used as an anti-oxidant for developer solutions. In the chemical and chemical-technical industry, sodium thiosulfate ( fixing salt ) is produced from sodium sulfite with the addition of sulfur . In the chemical fiber and textile industries it is used as a bleaching agent and to destroy active chlorine . It is also an aid in water treatment, because it acts as a corrosion protection by removing oxygen and is used to remove chlorine from service water. In the rubber and pulp industry , it helps to improve the quality of products. It is also an intermediate in the production of sodium dithionite .
- It is offered as an active ingredient against the formation of germs or algae.
- It is an antidote for nicotine poisoning .
- In addition to sodium dithionite, it is used as an active ingredient in the ink killer and is a component of stain removers .
Individual evidence
- ↑ Entry on E 221: Sodium sulphite in the European database for food additives, accessed on June 27, 2020.
- ↑ a b c d e f g h i j record with sodium sulfite in the GESTIS database of IFA , retrieved on July 13, 2018(JavaScript required) .
- ↑ a b c d Entry on sodium sulfite. In: Römpp Online . Georg Thieme Verlag, accessed on July 13, 2018.