What Is Sulfur Dioxide?
Sulfur dioxide is a colorless gas with a pungent odor, comprising of sulfur and oxygen.
Its chemical formula is SO2, with a molecular weight of 64.07 and a CAS number of 7446-09-5. Known as sulfurous acid gas or anhydrous sulfurous acid, sulfur dioxide occurs naturally in volcanic gases and mineral springs.
Structure of Sulfur Dioxide
The molecule has a bent structure with C2v symmetry, similar to that of ozone. The S-O bond distance is approximately 143 pm, and the bond angle is about 119°.
Properties of Sulfur Dioxide
1. Physical Properties
With a melting point of -75.5°C and a boiling point of -10°C, sulfur dioxide has a liquid specific gravity of 1.4. It is soluble in water and various organic solvents including acetone, ethanol, and benzene. It acts as both an oxidizing and reducing agent.
2. Other Characteristics
As a corrosive and toxic substance, sulfur dioxide can corrode metals and contribute to urban air pollution and acid rain through its presence in flue gas emissions from fossil fuel combustion.
Uses of Sulfur Dioxide
1. Food Additives
It serves as a preservative, bleaching agent, and antioxidant in alcoholic beverages and dried fruits, helping to prevent bacterial growth and oxidation.
2. Solvent
As a liquid, sulfur dioxide dissolves various substances and is used in nuclear magnetic resonance research and synthesis. It is available as liquefied gas in cylinders for commercial use.
3. Bleaching Agent
Employed as a reducing agent, it is used for bleaching paper, textiles, and other materials, although it does not offer long-lasting effects due to reoxidation.
4. Other
Additionally, sulfur dioxide is a precursor in the production of sulfuric acid and sodium sulfite and is used in insecticides, pesticides, pharmaceuticals, and petroleum refining.
Other Information on Sulfur Dioxide
1. Manufacturing Process
Produced by burning sulfur, hydrogen sulfide, or metal sulfides, sulfur dioxide is also a byproduct of cement production.
2. Regulatory Information
It is classified as hazardous under the Industrial Safety and Health Law and requires careful handling.
3. Handling and Storage Precautions
Precautions include storing in a cool, well-ventilated area, avoiding moisture and contact with incompatible materials, using protective gear, and ensuring proper ventilation during use.