Sodium hydrogen sulfite
| Density | ~ 1.34 g/cm3 |
| HS Code | 28321000 |
| Storage | store at 15 to 25 °C |
| SDS | available |
| R phrase | R 22-31 |
| S phrase | S 25-46 |
| Odour | slightly pungent |
| Form | liquid |
| Color | colorless to yellowish |
| p H value | 4.5 to 5.0 (22 g/l 20°C) |
| Solubility in water | soluble (20°C) |
| Boiling point | 146 °C |
| Melting point | _ 44 °C |
| Vapour pressure | 40 hPa |
| Thermal decomposition | > 150°C |
| Assay | ~ | 39 | % |
| Description | Conforms | ||
| Identification | Conforms | ||
| Solubility | Conforms |
Sodium hydrogen sulfite is a white, crystalline inorganic salt commonly used as a reducing agent, preservative, and antioxidant. It is also known as sodium bisulfite and plays an important role in food processing, water treatment, and chemical manufacturing.
🏭⚗️ Production
Sodium hydrogen sulfite is typically produced by bubbling sulfur dioxide (SO₂) gas into a cold, concentrated sodium hydroxide or sodium carbonate solution. The reaction is carefully controlled to produce the monosodium salt (NaHSO₃) rather than disodium sulfite (Na₂SO₃). The resulting solution can be concentrated and crystallized to yield solid sodium hydrogen sulfite.
🔬 Properties
The chemical formula of sodium hydrogen sulfite is NaHSO₃, with a molar mass of approximately 104.06 g/mol. It appears as a white to yellowish crystalline powder and has a slight sulfur dioxide odor. It is soluble in water, forming mildly acidic solutions, and is insoluble in alcohol. It is a weak acid salt and acts as a moderate reducing agent. Sodium hydrogen sulfite decomposes upon heating, releasing sulfur dioxide gas and leaving behind sodium sulfite or sulfate, depending on conditions.
🧪 Applications
Sodium hydrogen sulfite is widely used in the food industry as a preservative and antioxidant (E222), especially for preventing browning in fruits and vegetables and inhibiting microbial growth. In water treatment, it serves as a dechlorinating agent. In photography, it is used in developing solutions. It is also employed in chemical synthesis for sulfonation reactions, aldehyde protection, and in the purification of ketones and aldehydes. In laboratories, it is used to quench excess oxidizing agents and in analytical chemistry for various redox titrations.
⚠️ Safety
Sodium hydrogen sulfite can cause irritation to the eyes, skin, and respiratory system. Inhalation of its dust or vapors may trigger asthma-like symptoms or allergic reactions, especially in sensitive individuals. Ingestion can cause gastrointestinal distress and, in large amounts, may be harmful. The compound releases sulfur dioxide, a respiratory irritant, especially in moist environments. It should be handled with gloves and eye protection in well-ventilated areas and stored in tightly sealed containers, away from acids and heat sources.
