Potassium metabisulfite
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Other names
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Identifiers | |
3D model (
JSmol ) |
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ChemSpider | |
ECHA InfoCard
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100.037.072 |
E number | E224 (preservatives) |
PubChem CID
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RTECS number
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UNII | |
CompTox Dashboard (EPA)
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Properties | |
K2O5S2 | |
Molar mass | 222.31 g·mol−1 |
Appearance | White crystalline powder |
Odor | Pungent (sulfur dioxide) |
Density | 2.34 g/cm3 (solid) |
Melting point | 190 °C (374 °F; 463 K) decomposes |
450 g/L (20 °C) | |
Solubility | Insoluble in ethanol |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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Irritant, asthma risk |
GHS labelling: | |
Danger | |
H315, H318, H335 | |
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P310, P312, P321, P332+P313, P362, P403+P233, P405, P501 | |
NFPA 704 (fire diamond) | |
Safety data sheet (SDS) | ICSC 1175 |
Related compounds | |
Other anions
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Potassium bisulfite Potassium sulfite |
Other cations
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Sodium metabisulfite |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potassium metabisulfite, K2S2O5, also known as potassium pyrosulfite, is a white
Preparation and reactions
Potassium metabisulfite can be prepared by treating a solution of potassium hydroxide with sulfur dioxide.[2]
- 2 SO2 + 2 KOH → K2S2O5 + H2O
It decomposes at 190 °C, yielding potassium sulfite and sulfur dioxide:
- K2S2O5 → K2SO3 + SO2
Uses
It is used as a food additive, also known as E224.[3] It is restricted in use and may cause allergic reactions in some sensitive persons.[4]
Wine
Potassium metabisulfite is a common wine or must additive, in which it forms sulfur dioxide (SO2). Sulfur dioxide is a disinfectant. It also acts as a potent antioxidant, protecting both the color and delicate flavors of wine.
A high dose would be 3 grams of potassium metabisulfite per six-gallon bucket of must (yielding roughly 75 ppm of SO2) prior to fermentation; then 6 grams per six-gallon bucket (150 ppm of SO2) at bottling. Some countries regulate the SO2 content of wines.[5]
Winemaking equipment is sanitized by spraying with a 1% SO2 (2 tsp potassium metabisulfite per L) solution.
Beer
Potassium metabisulfite is sometimes used in the
Other uses
- Potassium metabisulfite is sometimes added to lemon juice as a preservative.
- Potassium metabisulfite is used in the textile industry for dyeing and cotton printing.
- Potassium metabisulfite is sometimes used to precipitate gold from solution in aqua regia (as an alternative to sodium sulfite).
- It is a component of certain photographic developers and solutions used in photographic processing, keeping active developing species from contact with oxygen.[6]
- It is used as a bleaching agent in the production of coconut cream.
- It is used in some pickles as a preservative.
- It is used in tint etching iron-based metal samples for microstructural analysis.[7]
- It is used in aam papad as a preservative.
See also
References
- ISBN 978-3527306732.
- ISBN 9780470132333.
- ^ List of E-number food additives
- ISBN 978-0-632-04601-0.
- ^ Gorman-McAdams, Mary (July 9, 2020). "The Truth About Sulfites in Wine & the Myths of Red Wine Headaches". The Kitchn. Retrieved February 10, 2024.
- ^ "Potassium Metabisulfite".
- ^ "Color Metallography". 2011-05-04.