Potassium sulfite

Structural formula
General
Surname	Potassium sulfite
other names	E 225 POTASSIUM SULFITE ( INCI )
Molecular formula	K 2 SO 3
Brief description	white solid
External identifiers / databases
CAS number 10117-38-1 7790-56-9 (dihydrate) EC number 233-321-1 ECHA InfoCard 100.030.279 PubChem 24958 ChemSpider 23332 Wikidata Q417109
properties
Molar mass	158.26 g · mol -1
Physical state	firmly
density	2.35 g cm −3 (20 ° C)
Melting point	decomposition
solubility	soluble in water (1060 g l −1 at 25 ° C) soluble in ethanol soluble in water (1070 g l −1 20 ° C dihydrate)
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium sulphite is a chemical compound that is used as a reducing agent in the chemical industry, especially in the photo industry.

Occurrence

Potassium sulfite is produced when black powder is burned .

Extraction and presentation

Sulphites are generally formed when sulfur dioxide reacts with water in the following two steps:

${\displaystyle \mathrm {SO_{2}+H_{2}O\longrightarrow HSO_{3}^{-}+H^{+}} }$

${\displaystyle \mathrm {HSO_{3}^{-}\leftrightharpoons SO_{3}^{2-}+H^{+}} }$

In order to produce potassium sulfite in this way, a potassium carbonate solution is mixed with sulfur dioxide and later further potassium carbonate is added.

When reacting sulphurous acid with potassium hydroxide :

${\displaystyle \mathrm {H_{2}SO_{3}+2\ KOH\longrightarrow K_{2}SO_{3}+2\ H_{2}O} }$

Chemical properties

Potassium sulfite is a potassium salt of sulphurous acid. It decomposes in air to form potassium sulphate.

use

Potassium sulfite is used as a component of photo chemicals ( developer solutions). It is also used as a food additive (e.g. in wine) and as a tanning accelerator.

See also

• Potassium disulfite

Individual evidence

1. ↑ Entry on POTASSIUM SULFITE in the CosIng database of the EU Commission, accessed on March 4, 2020.
2. ↑ ^{a b c d} Entry on potassium sulphite in the GESTIS substance database of the IFA , accessed on August 24, 2017(JavaScript required) .
3. ↑ ^{a b c} David R. Lide (Ed.): CRC Handbook of Chemistry and Physics : A ready-reference book of chemical and physical data . 90th edition. Taylor & Francis, Boca Raton, Florida 2009, ISBN 978-1-4200-9084-0 , pp. 4-83 .
4. ↑ Peter Kurzweil, Paul Scheipers: Chemistry . Springer-Verlag, 2012, ISBN 978-3-8348-8280-6 , p. 148 ( limited preview in Google Book search).
5. ^ ^{A b} Dale L. Perry: Handbook of Inorganic Compounds, Second Edition . CRC Press, 2011, ISBN 978-1-4398-1462-8 , pp. 333 ( limited preview in Google Book search).
6. ^ DN Rogers: The Chemistry of Photography From Classical to Digital Technologies . Royal Society of Chemistry, 2007, ISBN 978-0-85404-273-9 , pp. 54 ( limited preview in Google Book search).
7. ↑ Hans I. Bjelkhagen: Silver-halide recording materials for holography and their processing MATERIALS ... Springer Science & Business Media, 1995, ISBN 978-3-540-58619-7 , p. 124 ( limited preview in Google Book search).
8. ^ Gerhard Eisenbrand, Peter Schreier, Alfred Hagen Meyer: RÖMPP Lexikon Lebensmittelchemie, 2nd edition, 2006 . Georg Thieme Verlag, 2014, ISBN 3-13-179282-5 , p. 1326 ( limited preview in Google Book search).
9. ↑ Dr. Werner Baltes: Food chemistry . Springer-Verlag, 2013, ISBN 978-3-662-08281-2 , pp. 192 ( limited preview in Google Book search).