Sulfur

Sulfur is a nonmetallic chemical element with symbol S and atomic number 16. It occurs naturally in elemental form and in minerals and biological compounds.

Sulfur allotropes: Different structural forms of elemental sulfur, including rhombic and monoclinic crystals and polymeric chains. Sulfur changes structure with temperature, producing distinct crystalline and liquid forms.
Sulfuric acid: A strong mineral acid, H₂SO₄, produced on a large scale for industrial and chemical uses. Sulfur is converted into sulfuric acid, the element’s largest-volume industrial product.
Sulfur mining: The extraction of elemental sulfur or sulfur-bearing ores for industrial use. Mining and recovery turn naturally occurring sulfur deposits into commercial feedstock.
Acid rain: Precipitation acidified mainly by sulfuric and nitric acids formed from atmospheric emissions. Sulfur dioxide emissions can oxidize in air and contribute to acidifying rain.
Sulfur chemistry: The chemistry of sulfur and its compounds across multiple oxidation states and bonding patterns. Sulfur’s reactions range from sulfide formation to strongly oxidizing sulfuric acid.
Contact process: An industrial process that produces sulfuric acid by oxidizing sulfur dioxide over a catalyst. It is the principal route from sulfur-bearing feedstocks to sulfuric acid.
Frasch process: A method for extracting underground sulfur by melting it with superheated water and pumping it to the surface. It enabled large-scale recovery of sulfur from buried deposits.
Flue-gas desulfurization: Technologies that remove sulfur dioxide from exhaust gases, often using limestone or lime. Power plants use it to reduce sulfur pollution from burning sulfur-containing fuels.
Sulfide: A compound or ion in which sulfur has a low oxidation state, commonly −2. Sulfides are among sulfur’s most common forms in minerals and metal ores.
Haber process: An industrial method for synthesizing ammonia from nitrogen and hydrogen. Sulfur must be removed from feed gases because it poisons the process’s iron catalyst.

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