Potassium bisulfite is a chemical compound. It has the formula KHSO3. It acts as a preservative and antioxidant in food and wine.
| IUPAC name | Potassium hydrogen sulfite |
| Molecular formula | KHSO3 |
| CAS number | 7773-03-7 |
| Synonyms | Potassium bisulfite, potassium bisulphite, monopotassium salt, monopotassium sulfite, potassium hydrosulfite |
| InChI | InChI=1S/K.H2O3S/c;1-4(2)3/h;(H2,1,2,3)/q+1;/p-1 |
Potassium Bisulfite Properties
Potassium Bisulfite Formula
The formula of potassium bisulfite is KHSO3. This formula shows the ratio of potassium, hydrogen, sulfur, and oxygen atoms in one unit of potassium bisulfite. The formula can also be written as KH(SO3), which shows that potassium bisulfite is a salt of potassium and sulfurous acid (H2SO3).
Potassium Bisulfite Molar Mass
The molar mass of potassium bisulfite is 120.1694 g/mol. This means that one mole of potassium bisulfite has a mass of 120.1694 grams. The molar mass is calculated by adding the atomic masses of potassium, hydrogen, sulfur, and oxygen in the formula KHSO3.
Potassium Bisulfite Boiling Point
KHSO3 does not have a definite boiling point because it decomposes before reaching the boiling point. When heated above 190 °C, KHSO3 decomposes into potassium metabisulfite and water. The decomposition reaction is endothermic, meaning that it absorbs heat from the surroundings.
Potassium Bisulfite Melting Point
KHSO3 has a melting point of 190 °C, which is the same temperature at which it decomposes. Therefore, KHSO3 does not exist as a liquid under normal conditions. It is a white crystalline solid that dissolves in water.
Potassium Bisulfite Density g/ml
The density of KHSO3 is 2.103 g/ml at 20 °C. This means that one milliliter of KHSO3 has a mass of 2.103 grams. The density is influenced by the temperature and the concentration of the solution.
Potassium Bisulfite Molecular Weight
The molecular weight of KHSO3 is the same as its molar mass, which is 120.1694 g/mol. The molecular weight is the mass of one molecule of KHSO3, which is very small and cannot be measured directly. Molecular weight is useful for calculating the number of molecules in a given mass or volume of a substance.
Potassium Bisulfite Structure
KHSO3 has a structure that consists of K+ and HSO3- ions. The bisulfite ion has a tetrahedral shape with one hydrogen atom and three oxygen atoms bonded to a central sulfur atom. The sulfur atom has a double bond with one oxygen atom and a single bond with the other two oxygen atoms. The hydrogen atom is attached to one of the single-bonded oxygen atoms.
Potassium Bisulfite Solubility
KHSO3 is a chemical mixture that dissolves in water to form potassium ions and bisulfite ions. It has a sulfurous smell and a white solid appearance. It is soluble in water, with a solubility of 49 g/100 mL at 20 °C. It is used as a sterilizing agent in the production of alcoholic beverages.
| Appearance | White crystalline powder |
| Specific gravity | 2.103 |
| Color | White |
| Odor | SO2-like |
| Molar mass | 120.1694 g/mol |
| Density | 2.103 g/ml at 20 °C |
| Melting point | 190 °C (decomposes) |
| Boiling point | N/A (decomposes) |
| Flash point | N/A |
| Water solubility | 49 g/100 mL at 20 °C |
| Solubility | Insoluble in alcohol |
| Vapour pressure | N/A |
| Vapour density | N/A |
| pKa | 6.97 at 25 °C |
| pH | 4.5 (0.1 M solution) |
Potassium Bisulfite Safety and Hazards
KHSO3 is a corrosive substance that can cause severe skin burns and eye damage. It can also cause respiratory irritation and digestive tract burns if inhaled or swallowed. It is moisture sensitive and releases toxic sulfur dioxide gas when it reacts with acids. It should be handled with care and appropriate personal protective equipment. It should be stored in a dry and well-ventilated place, away from heat, sparks, flames, and incompatible materials. It should be disposed of in accordance with local regulations. In case of exposure, seek immediate medical attention and follow the first-aid measures on the safety data sheet.
| Hazard symbols | C (corrosive) |
| Safety description | S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. S36/37/39: Wear suitable protective clothing, gloves and eye/face protection. S45: In case of accident or if you feel unwell, seek medical advice immediately (show the label where possible). |
| UN IDs | UN 3260 |
| HS code | 2832 10 00 |
| Hazard class | 8 |
| Packing group | II |
| Toxicity | Oral LD50 (rat): 2340 mg/kg |
Potassium Bisulfite Synthesis Methods
Here are some methods to synthesize KHSO3:
- One method is to react with sulfur dioxide and potassium carbonate in a solution. To obtain KHSO3 crystals, pass sulfur dioxide through the solution until it stops evolving carbon dioxide, and then concentrate the solution.
- Another method is to react with potassium chloride and sulfuric acid in a solution. The reaction produces hydrogen chloride and KHSO3. After cooling, the solution actively undergoes filtration to separate the solid KHSO3.
- A third method is to react with potassium hydroxide and sulfuric acid in a solution. The reaction produces water and KHSO3. To purify the KHSO3, one can recrystallize the solution.
Potassium Bisulfite Uses
Here are some uses of KHSO3:
- Sterilizing agent: Used as a sterilizing agent in the production of alcoholic beverages. It prevents the growth of bacteria and fungi that can spoil wine or beer.
- Preservative: Used as a preservative and antioxidant in food. It inhibits the browning and oxidation of fruits, vegetables, juices, sauces, and dried foods.
- Reducing agent: Used as a reducing agent in organic chemistry. It can reduce aldehydes, ketones, nitro groups, sulfones, and sulfoxides to their corresponding alcohols, amines, sulfides, and sulfides.
- Bleaching agent: Used as a bleaching agent in the textile and paper industries. It can remove color and stains from fabrics and pulp.
- Used as a source of sulfur dioxide in various applications. It can release sulfur dioxide when heated or mixed with acids. Sulfur dioxide is a fumigant, a disinfectant, a solvent, and a catalyst.
Questions:
Q: How much potassium bisulfite to disinfect?
A: The amount of KHSO3 needed for disinfection depends on the concentration of the solution and the specific microorganisms being targeted. It is recommended to follow the instructions on the product label or seek guidance from a qualified professional.
Q: What is the formula for potassium bisulfite?
A: The chemical formula for potassium bisulfite is KHSO3.
Q: Is potassium bisulfite safe?
A: KHSO3 is generally safe when used according to instructions. However, it can be irritating to the skin, eyes, and respiratory system. It may also cause allergic reactions in some individuals. It is important to handle and store KHSO3 properly and to use protective equipment as needed.
Q: How long is potassium bisulfite good for?
A: The shelf life of KHSO3 depends on various factors such as the storage conditions, concentration, and purity of the product. Generally, it can last for several years if stored in a cool, dry place in a tightly sealed container.
Q: How do NaHSO3 and potassium iodate react to make an iodine reaction with starch equations?
A: The reaction of NaHSO3 and potassium iodate produces iodine, which can then react with starch to form a blue-black complex. The equations for the reactions are: 5NaHSO3 + KIO3 → 5NaHSO4 + KI + 3H2O + I2 I2 + starch → blue-black complex