Products
Sulfur dioxide is commercially available as a liquefied gas in compressed gas cylinders.
Structure and properties
Sulfur dioxide (SO2, 64.1 g/mol) exists as a colorless gas with a characteristic pungent and irritating sulfur odor that is soluble in water. The boiling point is -10°C. Sulfur dioxide is not combustible and is heavier than air. It is formed during the combustion of sulfur. This reaction is exothermic:
- S8 (sulfur) + 16 O2 (oxygen) 8 SO2 (sulfur dioxide)
Sulfur dioxide occurs naturally, for example, in volcanic gases and in a small concentration in the Earth’s atmosphere. Sulfur dioxide is used for the synthesis of sulfuric acid:
- 2 SO2 (sulfur dioxide) + 2 H2O (water) + O2 (oxygen) 2 H2SO4 (sulfuric acid)
With water, the extremely unstable sulfurous acid is formed, but it is undetectable in water:
- SO2 (sulfur dioxide) + H2O (water) H2SO3 (sulfurous acid)
Effects
Sulfur dioxide has antiseptic, antimicrobial, insecticidal, preservative, bleaching (decolorizing) and antioxidant properties. It is also harmful to many plants and to animals in higher concentrations. Sulfur dioxide is formed in the human body from the amino acid cysteine, for example, and performs physiological functions.
Areas of application
Fields of application include (selection):
- For the synthesis of sulfuric acid.
- As a preservative for the sulfurization of food, for example, for fruits, dried fruits and for wine (see also under sulfites).
- As a solvent and for chemical syntheses.
- Formerly used as a disinfectant (sulfur fumigations).
Adverse effects
Sulfur dioxide is toxic and highly inflammatory when inhaled. It causes severe skin burns, may irritate the respiratory tract and causes severe eye damage. The appropriate precautions in the safety data sheet must be observed. Sulfur dioxide is released during the combustion of fossil fuels because they contain sulfur in a relatively high concentration. This is particularly problematic if the sulfur is not removed before combustion. Global shipping, including cruise ships, is responsible for a high contribution of emissions. Sulfur dioxide can promote the development of respiratory diseases and have a negative impact on disease progression.
