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The term sulfide (sulphide in British English
British English

British English or UK English is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere....
) refers to several types of chemical compounds containing sulfur
Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
 in its lowest oxidation number
Oxidation number

The oxidation number of a central atom in a complex is the charge that it would have if all the ligands were removed along with the electron pairs that were shared with the central atom....
 of −2.

Formally, "sulfide" is the dianion, S2−, which exists in strongly alkaline aqueous solutions formed from H2S or alkali metal salts such as Li2S, Na2S, and K2S. Sulfide is exceptionally basic and, with a pKa > 14, it does not exist in appreciable concentrations even in highly alkaline water, being undetectable at pH < ~15 (8 M NaOH
Sodium hydroxide

Sodium hydroxide , also known as lye, caustic soda and sodium hydrate, is a caustic metallic Base . Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water, however, only the hydroxide ion is basic....
).






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The term sulfide (sulphide in British English
British English

British English or UK English is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere....
) refers to several types of chemical compounds containing sulfur
Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
 in its lowest oxidation number
Oxidation number

The oxidation number of a central atom in a complex is the charge that it would have if all the ligands were removed along with the electron pairs that were shared with the central atom....
 of −2.

Formally, "sulfide" is the dianion, S2−, which exists in strongly alkaline aqueous solutions formed from H2S or alkali metal salts such as Li2S, Na2S, and K2S. Sulfide is exceptionally basic and, with a pKa > 14, it does not exist in appreciable concentrations even in highly alkaline water, being undetectable at pH < ~15 (8 M NaOH
Sodium hydroxide

Sodium hydroxide , also known as lye, caustic soda and sodium hydrate, is a caustic metallic Base . Sodium hydroxide forms a strong alkaline solution when dissolved in a solvent such as water, however, only the hydroxide ion is basic....
). Instead, sulfide combines with electrons in hydrogen to form HS−, which is variously called hydrogen sulfide ion, hydrosulfide ion, sulfhydryl ion, or bisulfide ion. At still lower pH's (<7), HS− converts to H2S, hydrogen sulfide
Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the chemical formula Hydrogen2Sulfur. This colorless, toxic and flammable gas is partially responsible for the foul odor of egg and flatulence....
.

Aqueous solutions of transition metals cations react with sulfide sources (H2S, NaSH, Na2S) to precipitate solid sulfides. Such inorganic sulfides typically have very low solubility in water and many are related to minerals. One famous example is the bright yellow species CdS or "cadmium yellow". The black tarnish formed on sterling silver is Ag2S. Such species are sometimes referred to as salts. In fact the bonding in transition metal sulfides is highly covalent, which gives rise to their semiconductor
Semiconductor

A semiconductor is a material that has electrical conductivity between those of a Electrical conductor and an electrical insulation; it can vary over that wide range either permanently or dynamically....
 properties, which in turn is related to the practical applications of many sulfide materials.

In organic chemistry
Organic chemistry

Organic chemistry is a discipline within chemistry which involves the science study of the structure, properties, composition, chemical reaction, and preparation of chemical compounds that contain carbon....
, "sulfide" usually refers to the linkage C-S-C, although the term thioether
Thioether

A thioether is a functional group in organic chemistry that has the structure R1-S-R2 as shown on right. Like many other sulfur-containing compounds, Volatile organic compound thioethers characteristically have foul odors....
 is less ambiguous. For example, the thioether dimethyl sulfide
Dimethyl sulfide

Dimethyl sulfide or methylthiomethane is an Organosulfur compounds compound with the formula 2S. Dimethyl sulfide is a water-insoluble flammable liquid that boils at 37?C and has a characteristic disagreeable odor....
 is CH3-S-CH3. Polyphenylene sulfide (see below) has the empirical formula C6H4S. Occasionally, the term sulfide refers to molecules containing the -SH functional group
Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
. For example, methyl sulfide can mean CH3-SH. The preferred descriptor for such SH-containing compounds is thiol
Thiol

In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom . Being the sulfur analogue of an alcohol group , this functional group is referred to either as a thiol group or a sulfhydryl group....
 or mercaptan, i.e. methanethiol or methyl mercaptan.

Confusion arises from the different meanings of the term "disulfide
Disulfide

In chemistry, a disulfide usually refers to the structural unit composed of a linked pair of sulfur atoms. The disulfide anion is S22-....
". Molybdenum disulfide consists of separated sulfide centers, in association with molybdenum in the formal 4+ oxidation state. Iron disulfide on the other hand consists of S22−, or S−-S−, in association with iron in the formal 2+ oxidation state. Dimethyldisulfide has the connectivity CH3-S-S-CH3, whereas carbon disulfide
Carbon disulfide

Carbon disulfide is a colorless, volatile liquid with the chemical formula CS2. The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non-polar solvent....
 has no S-S linkages, being S=C=S.

Examples

Formula Melting point (°C) Boiling point (°C) CAS number
H2S hydrogen sulfide
Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the chemical formula Hydrogen2Sulfur. This colorless, toxic and flammable gas is partially responsible for the foul odor of egg and flatulence....
 		 -85,7 -60,20
CdS Cadmium sulfide
Cadmium sulfide

Cadmium Sulfur is a chemical compound with the formula CdS. Cadmium sulfide is yellow in colour and is a semiconductor. It exists in nature as two different minerals, greenockite and hawleyite....
 can be used in photocells. 		1750
Calcium
Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the earth's Crust ....
 polysulfide ("lime sulfur
Lime sulfur

In horticulture, lime sulfur is a mixture of calcium polysulfides formed by reacting calcium hydroxide with sulfur. It can be prepared by boiling calcium hydroxide and sulfur together with a small amount of surfactant....
") is a traditional fungicide
Fungicide

Fungicides are chemical compounds or biological organisms used to kill or inhibit fungus or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of Crop yield, quality and profit....
 in gardening
Gardening

Gardening is the practice of growing ornamental or useful plants. Ornamental plants are normally grown for their flowers, foliage, or overall appearance....
. 		 
CS2 Carbon disulfide
Carbon disulfide

Carbon disulfide is a colorless, volatile liquid with the chemical formula CS2. The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non-polar solvent....
 is sometimes used as a solvent
Solvent

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseous solute, resulting in a solution.The most common solvent in everyday life is water....
 in industrial chemistry. 		-111.6 46
PbS Lead sulfide
Lead sulfide

Lead sulfide is an ionic compound of lead and sulfur, having two possible proportions:*Lead sulfide, the ionic compound containing one lead atom and one sulfur atom....
 is used in infra-red sensors. 		1114
MoS2 Molybdenum disulfide
Molybdenum disulfide

Molybdenum disulfide is the inorganic chemistry with the chemical formula MoS2. This black crystalline sulfide of molybdenum occurs as the mineral molybdenite....
, the mineral molybdenite
Molybdenite

Molybdenite is a mineral of molybdenum disulfide, molybdenumsulfur2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure....
, is used as a catalyst to remove sulfur from fossil fuels.
Cl-CH2CH2-S-CH2CH2-Cl Mustard Gas, is a sulfide that has been used as a chemical weapon, the chloride on the molecule acts as a leaving group when in the presence of water and forms a sulfide-alcohol and HCl. 13 - 14 217
Ag2S Silver sulfide
Silver sulfide

Silver sulfide , Ag2S, is a black sulfide of silver. It is black and constitutes the tarnish that forms on silver when exposed to the hydrogen sulfide of the atmosphere....
 is formed on silver
Silver

Silver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal....
 electrical contacts operating in an atmosphere rich in hydrogen sulfide
Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the chemical formula Hydrogen2Sulfur. This colorless, toxic and flammable gas is partially responsible for the foul odor of egg and flatulence....
.
Na2S Sodium sulfide
Sodium sulfide

Sodium sulfide is the name used to refer to the chemical compound Na2S but more commonly its hydrate Na2S.9H2O....
 is an important industrial chemical, used in manufacture of kraft
Kraft process

The kraft process describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers. The process entails treatment of wood chips with a mixture of sodium hydroxide and sodium sulfide that break the bonds that link lignin to the cellulose....
 paper
Paper

Paper is thin material mainly used for writing upon, printing upon or packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
, dye
Dye

A dye can generally be described as a colored substance that has an Chemical affinity to the Wiktionary:substrate to which it is being applied....
s, leather tanning, crude petroleum processing, treatment of heavy metal
Heavy metals

A heavy metal is a member of an ill-defined subset of elements that exhibit metallic properties, which would mainly include the transition metals, some metalloids, lanthanides, and actinides....
 pollution
Pollution

Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms ....
, and others. 		920 1180
ZnS Zinc sulfide
Zinc sulfide

Zinc sulfide is a chemical compound with the chemical formula ZincSulfur. Zinc sulfide is a white- to yellow-colored powder or crystal. It is typically encountered in the more stable cubic form, known also as zinc blende or sphalerite....
 is used for lenses
Lens (optics)

A lens is an optics device with perfect or approximate axial symmetry which transmittance and refraction light, converging or diverging the beam....
 and other optical
Optics

Optics is the study of the behavior and properties of light including its optical phenomena with matter and its imaging by optical instruments....
 devices in the infrared
Infrared

Infrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light , but shorter than that of terahertz radiation and microwaves ....
 part of the spectrum
Electromagnetic spectrum

The electromagnetic spectrum is the range of all possible electromagnetic radiation frequencies. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation from that particular object....
. 		1185
ZnS Zinc
Zinc

Zinc is a metallic chemical element with the symbol Zn and atomic number 30. It is a first-row transition metal of the group 12 element of the periodic table....
 sulfide with a trace of copper is used for photoluminescent
Photoluminescence

Photoluminescence is a process in which a substance absorbs photons and then re-radiates photons. quantum mechanics, this can be described as an Quantum jump to a higher energy level and then a return to a lower energy state accompanied by the emission of a photon....
 strips for emergency lighting and luminous watch dials. 		 
Several metal sulfides are used as pigment
Pigment

A pigment is a material that changes the color of light it Reflection as the result of selective color absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which the material itself emits light....
s in art, although their use has declined somewhat due to their toxicity. Sulfide pigments include cadmium, mercury, and arsenic. 		 
C6H4S Polyphenylene sulfide is a polymer commonly called "Sulfar". Its repeating units are bonded together by sulfide (thioether) linkages.
SeS2 Selenium sulfide
Selenium sulfide

Selenium disulfide, also known as selenium sulfide or simply selenium sulfide, formula SeS2, is an antifungal agent often used in shampoos for the treatment of dandruff and seborrheic dermatitis associated in the scalp with Malassezia genus fungi....
 is an antifungal used in anti-dandruff preporations, such as Selsun Blue
Selsun Blue

Selsun Blue is a shampoo developed by Ross Laboratories , a subsidiary of Abbott Laboratories and later bought by Chattem, that functions as an over-the-counter substance treatment for dandruff....
. 		<100
FeS2 Iron disulfide occurs in pyrite
Pyrite

The mineral pyrite, or iron pyrite, is an iron sulfide with the chemical formula ironsulfur2. This mineral's metallic Lustre and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold due to its resemblance to gold....
 		 600


Natural occurrence

Many important metal
Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
 ore
Ore

An ore is a type of Rock that contains minerals such as gemstones and metals that can be extracted through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals, exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or crystalline formations of metals suc...
s are sulfides. Significant sulfide mineral
Sulfide mineral

A sulfide mineral is a mineral containing sulfide as the major anion. Sulfides are economically important as metal ores. The sulfide class also includes the selenide mineral, the telluride mineral, the arsenide mineral, the antimonide mineral, the bismuthinides, and the sulfosalts ....
s include:
  • arsenopyrite
    Arsenopyrite

    Arsenopyrite is an iron arsenic sulfide . It is a hard metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1....
     (arsenic
    Arsenic

    Arsenic is a well-known chemical element that has the symbol As and atomic number 33. Arsenic was first documented by Albertus Magnus in 1250....
     and iron
    Iron

    Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
    )
  • argentite
    Argentite

    Argentite was primarily treated as a mineral belonging to the galena group, cubic silver sulfide , occasionally found as uneven cubes and octahedron, but more often as dendritic or earthy masses, with a blackish lead-grey color and metallic lustre....
     (silver
    Silver

    Silver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal....
    )
  • chalcopyrite
    Chalcopyrite

    Chalcopyrite is a copper iron sulfide mineral that crystallizes in the tetragonal system. It has the chemical composition CuFeS2....
     (iron
    Iron

    Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
     and copper
    Copper

    Copper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity....
    )
  • cinnabar
    Cinnabar

    Cinnabar, sometimes written cinnabarite, is a name applied to red mercury sulfide , or native vermilion, the common ore of mercury . The name comes from the Greek language - "kinnabari" - used by Theophrastus, and was probably applied to several distinct substances....
     (mercury
    Mercury (element)

    Mercury , also called quicksilver or hydrargyrum , is a chemical element with the symbol Hg and atomic number 80. A heavy, silvery d-block metal, mercury is one of six elements that are liquid at or near room temperature and pressure....
    )
  • galena
    Galena

    Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals....
     (lead
    Lead

    Lead is a main-group Chemical element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metal ....
    )
  • molybdenite
    Molybdenite

    Molybdenite is a mineral of molybdenum disulfide, molybdenumsulfur2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure....
     (molybdenum
    Molybdenum

    Molybdenum , is a Group 6 element chemical element with the symbol Mo and atomic number 42. It has the List of elements by melting point melting point of any element....
    )
  • pentlandite
    Pentlandite

    Pentlandite is an iron-nickel sulfide, 9sulfur8. Pentlandite usually has a Ni:Fe ratio of close to 1:1. It also contains minor cobalt....
     (nickel
    Nickel

    Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge....
    )
  • pyrite
    Pyrite

    The mineral pyrite, or iron pyrite, is an iron sulfide with the chemical formula ironsulfur2. This mineral's metallic Lustre and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold due to its resemblance to gold....
     (iron
    Iron

    Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
    )
  • realgar
    Realgar

    Realgar, Polymorphism -As4S4, is an arsenic sulfide mineral. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment ....
     (arsenic
    Arsenic

    Arsenic is a well-known chemical element that has the symbol As and atomic number 33. Arsenic was first documented by Albertus Magnus in 1250....
    )
  • sphalerite
    Sphalerite

    Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron....
     (zinc
    Zinc

    Zinc is a metallic chemical element with the symbol Zn and atomic number 30. It is a first-row transition metal of the group 12 element of the periodic table....
    ) and
  • stibnite
    Stibnite

    Stibnite, sometimes called antimonite, is a sulfide mineral with the chemical formula antimony2sulfur3. This soft grey material crystallizes in an orthorhombic space group....
     (antimony
    Antimony

    Antimony is a chemical element with the symbol Sb and atomic number 51. A metalloid, antimony has four allotropy forms. The stable form of antimony is a blue-white metalloid....
    ).


Safety

Many metal sulfides are so insoluble in water that they are probably not very toxic. Some metal sulfides, when exposed to a strong mineral acid
Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
, including gastric acid
Gastric acid

Gastric acid is one of the main secretions of the stomach, together with several enzymes and intrinsic factor. Chemically it is an acid solution with a pH of 1 to 2 in the stomach lumen , consisting mainly of hydrochloric acid , and large quantities of potassium chloride and sodium chloride ....
s, will release toxic hydrogen sulfide.

Organic sulfides are highly flammable. When a sulfide burns, the fumes usually include toxic sulfur dioxide
Sulfur dioxide

Sulfur dioxide is the chemical compound with the formula SO2. It is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide....
 (SO2) gas.

Hydrogen sulfide, some of its salts, and almost all organic sulfides have a strong and putrid stench; rotting biomass releases these. Mercaptans
Thiol

In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom . Being the sulfur analogue of an alcohol group , this functional group is referred to either as a thiol group or a sulfhydryl group....
, in particular, are the strongest-smelling substances known.

Corrosion induced by sulfide


Dissolved free sulfides (H2S, HS- and S2-) are very aggressive species for the corrosion of many metals such as, e.g., steel, stainless steel, and copper. Sulfides present in aqueous solution are responsible for stress corrosion cracking
Stress corrosion cracking

Stress corrosion cracking is the unexpected sudden failure of normally ductile metals or tough thermoplastics subjected to a tensile stress in a corrosion environment, especially at elevated temperature in the case of metals....
 (SCC) of steel, and is also known as sulfide stress cracking. Corrosion is a major concern in many industrial installations processing sulfides: sulfide ore mills, deep oil well
Oil well

An oil well is a general term for any boring through the Earth's surface designed to find and produce petroleum Petroleum hydrocarbons. Usually some natural gas is produced along with the oil, and a well designed to produce mainly or only gas may be termed a gas well....
s, pipeline transporting soured oil
Oil

An oil is a chemical substance that is in a viscosity liquid state at room temperature or slightly warmer, and is both hydrophobic and lipophilic ....
, Kraft paper
Kraft paper

Kraft paper is paper produced by the kraft process from wood pulp. It is strong and relatively coarse. Kraft paper is usually a brown colour but can be bleached to produce white paper....
 factories. Microbially-induced corrosion
Microbial corrosion

Microbial corrosion, also called bacterial corrosion, bio-corrosion, microbiologically-influenced corrosion, or microbially-induced corrosion , is corrosion caused or promoted by microorganisms, usually chemoautotrophs....
 (MIC
MIC

MIC may refer to:...
) or biogenic sulfide corrosion
Biogenic sulfide corrosion

Biogenic Sulfide Corrosion is a bacterially mediated process of forming hydrogen sulfide gas and the subsequent conversion to sulfuric acid that attacks concrete and steel within wastewater environments....
 are also caused by sulfate reducing bacteria producing sulfide.

Oxidation of sulfide can also form thiosulfate
Thiosulfate

Thiosulfate is an oxyanion of sulfur produced by the reaction of sulfite ions with elemental sulfur in boiling water. Thiosulfate occurs naturally in hot springs and geysers, and is produced by certain biochemical processes....
 (S2O32-) an intermediate species responsible for severe problems of pitting corrosion
Pitting corrosion

Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the creation of small holes in the metal. The driving power for pitting corrosion is the lack of oxygen around a small area....
 of steel and stainless steel while the medium is also acidified by the production of sulfuric acid when oxidation is more advanced.

See also

  • Biogenic sulfide corrosion
    Biogenic sulfide corrosion

    Biogenic Sulfide Corrosion is a bacterially mediated process of forming hydrogen sulfide gas and the subsequent conversion to sulfuric acid that attacks concrete and steel within wastewater environments....
  • Sulfide stress cracking
  • Sulfate
    Sulfate

    In inorganic chemistry, a sulfate is a salt of sulfuric acid....
  • Sulfidation
  • Sulfite
    Sulfite

    Sulfites are chemical compound that contain the sulfite ion sulfuroxygen32- ....
  • Thioether
    Thioether

    A thioether is a functional group in organic chemistry that has the structure R1-S-R2 as shown on right. Like many other sulfur-containing compounds, Volatile organic compound thioethers characteristically have foul odors....
  • Thiosulfate
    Thiosulfate

    Thiosulfate is an oxyanion of sulfur produced by the reaction of sulfite ions with elemental sulfur in boiling water. Thiosulfate occurs naturally in hot springs and geysers, and is produced by certain biochemical processes....
  • Dithionite
    Dithionite

    The dithionite ion, S2O42-, is a sulfur oxoanion formally derived from the hypothetical compound dithionous acid, H2S2O4....