| Customization: | Available |
|---|---|
| CAS No.: | 16731-55-8 |
| Formula: | K2s2o5 |
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Potassium metabisulfite can be prepared by treating a solution of potassium hydroxide with sulfur dioxide.
2 SO2 + 2 KOH → K2S2O5 + H2OIt decomposes at 190 °C, yielding potassium sulfite and sulfur dioxide:
It is used as a food additive, also known as E224.It is restricted in use and may cause allergic reactions in some sensitive persons.
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.
Winemaking equipment is sanitized by spraying with a 1% SO2 (2 tsp potassium metabisulfite per L) solution.
Potassium metabisulfite is sometimes used in the brewing industry to inhibit the growth of wild bacteria and fungi. This step is called 'stabilizing'. It is also used to neutralize monochloramine from tap water. It is used both by homebrewers and commercial brewers alike. It is not used as much for brewing beer, because the wort is almost always boiled, which kills most microorganisms.
| Test item | Unit | Specification | Test datum |
| K2S2O5 | g/100g | ≥97.2 | 97.3 |
| SO2 | g/100g | ≥56.0 | 56.14 |
| K2S2O3 | g/100g | <= 0.1 | 0.002 |
| Na | g/100g | <= 2 | 0.090 |
| Cl | g/kg | <= 0.5 | 0.01 |
| pH-value(10%solution) | - | 3.8-4.8 | 4.4 |
| heavy metal(measured by Pb) | mg/kg | <=10 | 8 |
| As | mg/kg | <= 1 | 0.05 |
| Cu | mg/kg | <=1 | 0.3 |
| Fe | mg/kg | <=5 | 3.6 |
| Hg | mg/kg | <=0.1 | 0.02 |
| Pb | mg/kg | <=1 | 0.5 |
| Se | mg/kg | <=1 | 0.1 |
| Zn | mg/kg | <= 1 | 0.3 |
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