Sulfur dioxide

Sulfur dioxide is a colorless, pungent gas with the formula SO₂. It forms during sulfur combustion and is used in industry and food preservation.

Sulfur dioxide oxidation: The conversion of sulfur dioxide into sulfur trioxide or sulfate through reactions with oxidants. Atmospheric oxidation transforms emitted SO₂ into sulfate particles and contributes to acid deposition.
Contact process: The industrial method for manufacturing sulfuric acid by oxidizing sulfur dioxide to sulfur trioxide. It is the dominant route that turns SO₂ into bulk sulfuric acid.
Acid rain: Precipitation acidified mainly by sulfuric and nitric acids formed from atmospheric pollutants. SO₂ oxidation produces sulfuric acid that can return to Earth in precipitation.
Coal combustion: The burning of coal to release heat, often producing sulfur dioxide when coal contains sulfur. Sulfur impurities in coal become SO₂ during combustion.
Sulfur trioxide: A colorless, reactive compound with the formula SO₃ and the principal precursor of sulfuric acid. Adding one oxygen atom changes SO₂ into the more reactive SO₃.
Sulfurous acid: An aqueous solution of sulfur dioxide, commonly represented by the formula H₂SO₃. Dissolved SO₂ forms acidic aqueous species that shape its behavior in clouds and liquids.
Sulfur dioxide in winemaking: The use of sulfur dioxide and sulfites to limit oxidation and microbial growth in wine. Winemakers use dissolved SO₂ to protect wine while managing its concentration and effects.
Particulate matter: A mixture of tiny solid particles and liquid droplets suspended in air. Atmospheric conversion of SO₂ produces sulfate particles, a component of fine particulate pollution.
Oil refining: The industrial processing of crude oil into fuels and other products. Sulfur removed from petroleum streams can be converted into SO₂ during refining and fuel use.
Hydrogen sulfide: A toxic, flammable gas with the formula H₂S and a characteristic rotten-egg odor. Despite containing sulfur, H₂S is a reduced, combustible gas rather than an oxidized SO₂ pollutant.

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