Sulfide

Sulfides are salts or alkyl or aryl derivatives of hydrogen sulfide (H2S). The salts belonging to the group of substances of the metal -sulfur compounds and containing the sulfide anion as a component S2. The anion itself is also briefly referred to as sulfide. Metal sulfides provide in mineralogy an important group of ores dar. In the analysis, the metal sulfides belong to the so-called hydrogen sulfide group and the ammonium sulfide group.

The alkyl and aryl sulfides are some of the organic compounds ( organic group: R- ) and have the structure R-S - R '. They are also referred to as thioether.

Sulfide minerals

Along with metal or semi-metal cations are formed approximately 600 sulfide minerals, mostly distinguished by characteristic colors and line colors. They include a number of important ores, so that inorganic sulfides because of their sometimes high metal content as raw materials in the recovery, among others serve of iron, copper, lead, zinc, mercury, arsenic and antimony. Here are some sulfidic minerals:

• Galena and galena (PbS )
• Bornite ( bornite or copper Lazur ) ( Cu5FeS4 )
• Covellite (copper (II ) sulfide ) ( CuS )
• Chalcopyrite ( chalcopyrite or chalcopyrite ) ( CuFeS2 )
• Pyrite ( fool's gold or fool's gold ) ( FeS2 )
• Stibnite (antimony gloss or gray antimony ) ( Sb2S3 )
• Sphalerite or zinc blende (ZnS )
• Cinnabar or vermilion ( HgS )
• Molybdenite and molybdenite (molybdenum (IV ) sulfide )

The chemical element is sulfur, similar to the projecting in the same main group of the Periodic Table of oxygen, the doubly negatively charged anion sulfide S2.

The sulphides of the alkali and alkaline earth metals can form by the addition of sulfur to sulfide -free electron pairs of polysulfides. Heavy metal salts form insoluble precipitates with sulfide solutions - a property that one uses for analytical chemistry in cation separation transition.

Polymetallic sulphides which occur at hydrothermal vents of the deep sea, may constitute a source of raw materials for a variety of precious and rare metals in the future. Germany has a 2013 license to degradation of marine resources in the Indian Ocean in Madagascar requested.

Chemical Properties

Metal sulfides such as iron sulfide must be considered as salts of hydrogen sulphide. Sulfides react accordingly to the respective metal salts and hydrogen sulfide ( up to chlorides in hydrochloric acid) (H2S), which is noticeable by its very unpleasant smell ( rotten eggs ) with correspondingly stronger acids ( eg hydrochloric acid).

In aqueous solution, the sulphide ion S2 - pH - dependent protonation. In the pH range of 9-11 sulfide is mainly present as a hydrogen sulfide anion ( HS- ). This is, inter alia, in the cation separation passage used in the hydrogen sulfide and ammonium sulfide group, since the pH -dependent sulfide ion concentration allows a gradual precipitation of the different soluble sulfides.

For hydrogen sulfide group namely include only those elements that already in acidic sparingly soluble sulfides form with the release agent ( precipitation reaction; sulfide examples in the photograph, from left to right: precipitation with manganese ( II) -, cadmium (II ) -, copper ( II) - zinc (II) -, antimony ( III) -, bismuth (III) -, lead ( II) - and tin (IV ) cations ). For the ammonium sulfide group include the precipitable only in basic medium metal sulfides. They are soluble with the addition of acids (see above). In addition to the sulfides, there is the related to them thio and sulfosalts. Here are oxygen atoms has been replaced by sulfur atoms (example: Natriumthiostannat and thioantimonat, sodium thiosulfate / fixer ).

Proof

Sulfide ions (S2 - ) can be detected with lead acetate paper, with a black color of the paper occurs, caused by lead sulfide:

A further possibility is that acidification of a solid sample with a strong acid. The result is a hideous, characteristic odor of rotten eggs, caused by the gas hydrogen sulfide, which could be displaced from the sulfide with the acid.

With sodium nitroprusside forms in weakly alkaline solution, a violet solution of [ Fe ( CN) 5NOS ] 4 -.

Use

Sulfide metal precipitation

Chemical precipitation of metal sulfides not only plays a role in the industrial production processes, for example in the manufacture of pigments, but also waste water treatment processes. The low solubility of the metal sulfide is used in order to obtain the smallest possible residual metal concentrations. Sulfides are usually considerably less soluble than the hydroxides, such as: lead sulfide, cadmium sulfide, iron sulfide, copper sulfide, nickel sulfide, silver sulfide, or zinc sulfide. As sulfidic precipitant is used in the control of sodium sulfide or sodium hydrosulfide.

Molybdenum disulfide

Molybdenum (IV ) sulfide ( MoS 2 ) is added as powder lubricants, and improves run-flat.

Organic sulfides

Many odor of natural flavorings are organic sulfides ( eg coffee ). The natural amino acid methionine is a sulfide. For organic sulfides see thioether.

Importance for the environment

Sulfides play an important role in the formation of acid mine waters. Acid mine waters are formed when the present in the rocks sulphide minerals are exposed to oxidizing conditions. The iron sulfides are present in the mining areas, most commonly pyrite ( FeS2 ) and marcasite ( FeS 2 ).