Potassium bisulfite
| Names | |
|---|---|
| IUPAC name
Potassium hydrogen sulfite
| |
| Other names
E228
Monopotassium sulfite Potassium bisulphite Sulfurous acid, monopotassium salt | |
| Properties | |
| KHSO3 | |
| Molar mass | 120.1561 g/mol |
| Appearance | White crystalline powder |
| Odor | Sulfurous |
| Melting point | 190 °C (374 °F; 463 K) (decomposes) |
| Boiling point | Decomposes |
| 49 g/100 mL (20 °C) 115 g/100 mL (100 °C) | |
| Solubility | Insoluble in alcohols, benzene, toluene |
| Hazards | |
| Safety data sheet | CAMEO (solution) |
| Flash point | Non-flammable |
| Related compounds | |
| Related compounds
|
Potassium sulfite Potassium bisulfate |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Potassium bisulfite or potassium hydrogen sulfite is a chemical compound with the chemical formula KHSO3. The compound is commonly used in food industry, for sterilizing wine, as food additive E228. While it can be found as solid, it is more commonly encountered as solution.
Contents
Properties
Chemical
Potassium bisulfite oxidizes in air to potassium bisulfate.
- KHSO3 + ½ O2 → KHSO4
The reaction occurs faster if water is present.
Addition of a base raises the pH, converting the compound in potassium sulfite.
- KHSO3 + KOH → K2SO3 + H2O
Evaporating an aq. solution of potassium bisulfite saturated with sulfur dioxide yields potassium metabisulfite:
- 2 KHSO3 ⇌ H2O + K2S2O5
Physical
Potassium bisulfite is a white solid, with a sulfurous smell, soluble in water.
Availability
Potassium bisulfite is sold as both solid and solution, with the latter being more available. Make sure to check the product label/designation, as some products labeled as potassium bisulfite are actually potassium metabisulfite.
It is available as the food additive E228.
Preparation
Can be prepared by bubbling and excess of sulfur dioxide through a solution of potassium carbonate or potassium hydroxide. The excess sulfur dioxide is removed, usually by adding KOH until the right pH, then the solution is dried in an airless atmosphere, to prevent the sulfite from oxidizing to sulfate.
- K2CO3 + SO2 → K2SO3 + H2O + CO2
- 2 KOH + SO2 → K2SO3 + H2O
Projects
- Reducing agent
- Make sulfur dioxide
- Make potassium bisulfate
- Make hydroxylamine
Handling
Safety
Potassium bisulfite releases toxic sulfur dioxide gas, especially in contact with acids. Work in a well ventilated area or fumehood.
Storage
Should be stored in closed, air-tight bottles.
Disposal
Can be neutralized with bleach or hydrogen peroxide, then with a base to potassium sulfate.
