Sulfide

sulfide

[′səl‚fīd]

(chemistry)

Any compound with one or more sulfur atoms in which the sulfur is connected directly to a carbon, metal, or other nonoxygen atom; for example, sodium sulfide, Na₂S.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Sulfide

 

any of several compounds of sulfur with more electropositive elements; sulfides may be regarded as salts of hydrogen sulfide, H₂S. There are two sulfide series: the normal sulfides, with the general formula M₂S, and the acid sulfides, with the general formula MHS, where M is a monovalent metal.

Sulfides of alkali metals are colorless and dissolve readily in water. Their aqueous solutions are strongly hydrolyzed and exhibit a basic reaction. The action of dilute acids on such sulfides results in liberation of H₂S. Sulfides of alkaline-earth metals are colorless, with sparing solubility in water. They liberate H₂S in humid air. In other properties they are similar to the sulfides of alkali metals. Both types of sulfides oxidize readily to sulfates.

Sulfides of heavy metals are virtually insoluble in water. Almost all of them are black or brownish black, with the exception of white ZnS, pinkish MnS, yellow CdS, reddish orange Sb₂S₃, and yellow SnS₂. The differing relationship of sulfides to acids and ammonium sulfide is used in chemical analysis.

Many elements form polysulfides, with the general formula M₂S_x. These compounds decompose upon heating, with the formation of normal sulfides. Na, K, NH⁺₄, Ca, Sr, and Ba have a particular tendency to form polysulfides.

Sulfides are obtained by (1) direct addition of elements, (2) reaction of aqueous solutions of salts with H₂S or (NH₄)₂S, (3) reaction of hydroxides with H₂S, and (4) reduction of sulfates by coal during roasting.

Many sulfides have great practical importance: Na₂S, CaS, and BaS are used in the leather industry for tanning, and polysulfides of calcium and barium are used to combat agricultural pests. In addition, PbS, CdS, and ZnS are used as semiconductor materials, and crystals of these and other sulfides are used as semiconductor laser materials. The sulfides of the alkaline-earth metals, along with ZnS and CdS, are bases for luminophors, MoS₂ is a solid lubricant, (NH₄)₂S is an important reagent in qualitative analysis, and FeS₂ is a raw material for the production of sulfuric acid.

I. K. MALINA

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.