In chemistry, a sulfide (sulphide in British and Canadian English) is a combination of sulfur with an oxidation number of -2, with another chemical element or a radical thereof. A few covalent sulfur compounds, such as carbon disulfide (CS₂) and hydrogen sulfide (H₂S) are also considered to be sulfides. It is also known as a thioether.

Hydrogen sulfide gas has the odor of rotten eggs, and is also highly toxic. It is formed biologically in the sediments of swamps and in the treatment of sewage sludge by anaerobic digestion of sulfur containing proteins, or bacterial reduction of sulfates. It also occurs in the emissions of some volcanoes, and as a byproduct of some industrial processes.

Uses

• Cadmium disulfide (CdS₂) can be used in photocells.
• Calcium polysulfide ("lime sulfur ") is a traditional fungicide in gardening.
• Carbon disulfide (CS₂) is sometimes used as a solvent in industrial chemistry.
• Lead sulfide (PbS) is used in infra-red sensors.
• Silver sulfide (Ag₂S) is formed on silver electrical contacts operating in an atmosphere rich in Hydrogen sulfide.
• Sodium sulfide (Na₂S) is an important industrial chemical, used in manufacture of kraft paper, dyes, leather tanning, crude petroleum processing, treatment of heavy metal pollution, and others.
• Zinc sulfide (ZnS) is used for lenses and other optical devices in the infrared part of the spectrum.
• Zinc sulfide with a trace of copper is used for photoluminescent strips for emergency lighting and luminous watch dials.
• Several metal sulfides are used as pigments in art, although their use has declined somewhat due to their toxicity. Sulfide pigments include cadmium, mercury, and arsenic.

Natural occurrence

Many important metal ores are sulfides. Significant sulfide minerals include:

• arsenopyrite (arsenic and iron)
• argentite (silver)
• chalcopyrite (iron and copper)
• cinnabar (mercury)
• galena (lead)
• molybdenite (molybdenum)
• pentlandite (nickel)
• pyrite (iron)
• realgar (arsenic)
• sphalerite (zinc) and
• stibnite (antimony).

Safety

Many sulfides are significantly toxic by inhalation or injection, especially if the metal ion is toxic. Additionally many sulfides, when exposed to a strong mineral acid, will release toxic hydrogen sulfide - and this includes your stomach acids!

Also, many sulfides are somewhat flammable, and a few are highly flammable. When a sulfide burns, the fumes usually include toxic sulfur dioxide (SO₂) gas.

See also

• sulfate
• sulfite