Sulfur S

Discovery

Because it occurs naturally in pure form, sulfur was known to ancient peoples. Called brimstone, 'burning stone', it appears in ancient texts; Homer describes it being burned to fumigate a house. Sulfur was used in medicines, bleaching and, from about the ninth century in China, as one of the three ingredients of gunpowder.

Alchemists regarded sulfur as one of the fundamental principles of matter. In 1777 Antoine Lavoisier argued that it was an element rather than a compound, and in 1809 Joseph Louis Gay-Lussac and Louis Jacques Thénard confirmed this.

Large-scale mining changed in the 1890s when Herman Frasch developed a method of melting underground sulfur with superheated water and pumping it to the surface. Today, however, most sulfur is recovered as a by-product of cleaning natural gas and crude oil.

Origin of the name

The name comes from the Latin sulpur or sulfur. In 1990 IUPAC adopted the spelling sulfur as standard, though sulphur remains common in British English. The symbol is S.

Main uses

• Sulfuric acid: most sulfur is converted to sulfuric acid, which is used to make fertilisers, process ores, refine petroleum and fill lead-acid batteries.
• Rubber: heating rubber with sulfur, a process called vulcanisation that Charles Goodyear developed in 1839, makes tyres tough and elastic.
• Agriculture: sulfur is a plant nutrient and a traditional fungicide.
• Medicines and chemicals: sulfa drugs were among the first antibacterial medicines; sulfur is also used in matches, fireworks and detergents.

Isotopes

Sulfur has four stable isotopes: sulfur-32 (about 95 percent), sulfur-33, sulfur-34 (about 4 percent) and sulfur-36. Small anomalies in the ratios of these isotopes in very old rocks are among the strongest evidence that Earth's early atmosphere had almost no oxygen. The radioactive sulfur-35 (half-life about 87 days) is used to label proteins and to trace sulfur in the environment.

In everyday life

Sulfur is part of the amino acids methionine and cysteine, and bridges between sulfur atoms help give hair and proteins their shape. The smell of garlic, onions, skunk spray and rotten eggs all come from sulfur compounds.

Hydrogen sulfide is toxic in higher concentrations and can deaden the sense of smell, making it more dangerous. Sulfur dioxide from burning coal and oil causes acid rain, which is why fuels are now desulfurised.