Most often in sulfur chemistry and in biochemistry, the disulfide term is commonly ascribed to the sulfur analogue of the peroxide –O–O– bond. Dimethyldisulfide has the chemical binding CH 3–S–S–CH 3, whereas carbon disulfide has no S–S bond, being S=C=S (linear molecule analog to CO 2). Iron disulfide ( pyrite, FeS 2) on the other hand consists of S 2−Ģ, or −S–S − dianion, in association with divalent iron in the formal +2 oxidation state (ferrous ion: Fe 2+). Molybdenum disulfide (MoS 2) consists of separated sulfide centers, in association with molybdenum in the formal +4 oxidation state (that is, Mo 4+ and two S 2−). methanethiol, or methyl mercaptan.Ĭonfusion arises from the different meanings of the term " disulfide".
The preferred descriptor for such SH-containing compounds is thiol or mercaptan, i.e. For example, methyl sulfide can mean CH 3–SH. Occasionally, the term sulfide refers to molecules containing the –SH functional group. Polyphenylene sulfide (see below) has the empirical formula C 6H 4S. For example, the thioether dimethyl sulfide is CH 3–S–CH 3. In organic chemistry, "sulfide" usually refers to the linkage C–S–C, although the term thioether is less ambiguous. Oxidation of sulfide can also form thiosulfate ( Sģ) an intermediate species responsible for severe problems of pitting corrosion of steel and stainless steel while the medium is also acidified by the production of sulfuric acid when oxidation is more advanced.
This kind of deterioration is a major process affecting sewer systems worldwide and leading to very high rehabilitation costs. Biogenic sulfuric acid reacts with sewerage materials and most generally causes mass loss, cracking of the sewer pipes and ultimately, structural collapse. Microbially-induced corrosion (MIC) or biogenic sulfide corrosion are also caused by sulfate reducing bacteria producing sulfide that is emitted in the air and oxidized in sulfuric acid by sulfur oxidizing bacteria. Corrosion is a major concern in many industrial installations processing sulfides: sulfide ore mills, deep oil wells, pipelines transporting soured oil, Kraft paper factories. Sulfides present in aqueous solution are responsible for stress corrosion cracking (SCC) of steel, and is also known as sulfide stress cracking.
#Hydrogen sulfide free
Significant examples include: argentite ( silver sulfide), cinnabar ( mercury sulfide), galena ( lead sulfide), molybdenite ( molybdenum sulfide), pentlandite ( nickel sulfide), realgar ( arsenic sulfide), and stibnite ( antimony), sphalerite ( zinc sulfide), and pyrite ( iron disulfide), and chalcopyrite ( iron- copper sulfide).ĭissolved free sulfides (H 2S, HS − and S 2−) are very aggressive species for the corrosion of many metals such as steel, stainless steel, and copper. The fungus Aspergillus niger plays a role in the solubilization of heavy metal sulfides. Several have practical applications as pigments, in solar cells, and as catalysts.
In fact, the bonding in transition metal sulfides is highly covalent, which gives rise to their semiconductor properties, which in turn is related to the deep colors. Such species are sometimes referred to as salts. The black tarnish formed on sterling silver is Ag 2S. One famous example is the bright yellow species CdS or " cadmium yellow". Such inorganic sulfides typically have very low solubility in water, and many are related to minerals with the same composition (see below). Metal sulfides react with halogens, forming sulfur and metal salts.Ĩ MgS + 8 I 2 → S 8 + 8 MgI 2 Metal derivatives Īqueous solutions of transition metals cations react with sulfide sources (H 2S, NaHS, Na 2S) to precipitate solid sulfides. Depending on the conditions, the oxidation can produce elemental sulfur, polysulfides, polythionates, sulfite, or sulfate.
Oxidation of sulfide is a complicated process. Upon treatment with an acid, sulfide salts convert to hydrogen sulfide: Instead sulfide converts to hydrosulfide: The sulfide ion, S 2−, does not exist in aqueous alkaline solutions of Na 2S.
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