CARBON BISULPHIDE

carbon bisulphide, cs2, a chemical product first discovered in 1796 by w.a. lampadius, who obtained it by heating a mixture of charcoal and pyrites. it may be more conveniently prepared by passing the vapour of sulphur over red hot charcoal, the uncondensed gases so produced being led into a tower containing plates over which a vegetable oil is allowed to flow in order to absorb any carbon bisulphide vapour, and then into a second tower containing lime, which absorbs any sulphuretted hydrogen. the crude product is very impure and possesses an offensive smell; it may be purified by forcing a fine spray of lime water through the liquid until the escaping water is quite clear, the washed bisulphide being then mixed with a little colourless oil and distilled at a low temperature. for further methods of purification see j. singer (_journ. of soc. chem. ind._, 1889, p. 93), th. sidot (_jahresb._, 1869, p. 243), e. allary (_bull. de la soc. chim._, 1881, 35, p. 491), e. obach (_jour. prak. chem._, 1882 (2), 26, p. 282). when perfectly pure, carbon bisulphide is a colourless, somewhat pleasant smelling, highly refractive liquid, of specific gravity 1.2661 (18 deg./4 deg.) (j.w. bruhl) or 1.29215 (0 deg./4 deg.) (t.e. thorpe). it boils at 46.04 deg. c. (t.e. thorpe, _journ. chem. soc._, 1880, 37, p. 364). its critical temperature is 277.7 deg. c., and its critical pressure is 78.1 atmos. (j. dewar, _chem. news_, 1885, 51, p. 27). it solidifies at about -116 deg.c., and liquefies again at about -110 deg.c. (k. olszewski, _jahresb._, 1883, p. 75). it is a mono-molecular liquid (w. ramsay and j. shields, _jour. chem. soc._, 1893, 63, p. 1089). it is very volatile, the vapour being heavy and very inflammable. it burns with a pale blue flame to form carbon dioxide and sulphur dioxide. it is almost insoluble in water, but mixes in all proportions with absolute alcohol, ether, benzene and various oils. it is a good solvent for sulphur, phosphorus, wax, iodine, &c. it dissociates when heated to a sufficiently high temperature. a mixture of carbon bisulphide vapour and nitric oxide burns with a very intense blue-coloured flame, which is very rich in the violet or actinic rays. when heated with water in a sealed tube to 150 deg. c. it yields carbon dioxide and sulphuretted hydrogen. zinc and hydrochloric acid reduce it to tri-thioformaldehyde (ch2s)3 (a. girard, _comptes rendus_, 1856, 43, p. 396). when passed through a red-hot tube with chlorine it yields carbon tetrachloride and sulphur chloride (h. kolbe). potassium, when heated, burns in the vapour of carbon bisulphide, forming potassium sulphide and liberating carbon. in contact with chlorine monoxide it forms carbonyl chloride and thionyl chloride (p. schutzenberger, _ber._, 1869, 2, p. 219). when passed with carbon dioxide through a red-hot tube it yields carbon oxysulphide, cos (c. winkler), and when passed over sodamide it yields ammonium thiocyanate. a mixture of carbon bisulphide vapour and sulphuretted hydrogen, when passed over heated copper, gives, amongst other products, some methane. carbon bisulphide slowly oxidizes on exposure to air, but by the action of potassium permanganate or chromic acid it is readily oxidized to carbon dioxide and sulphuric acid. by the action of aqueous alkalis, carbon bisulphide is converted into a mixture of an alkaline carbonate and an alkaline thiocarbonate (j. berzelius, _pogg. ann._, 1825, 6, p. 444), 6kho + 3cs2 = k2co3 + 2k2cs3 + 3h2o; on the other hand, an alcoholic solution of a caustic alkali converts it into a xanthate (a. vogel, _jahresb._, 1853, p. 643), cs2 + kho + r.oh = h2o + ro.cs.sk. aqueous and alcoholic solutions of ammonia convert carbon bisulphide into ammonium dithiocarbamate, which readily breaks down into ammonium thiocyanate and sulphuretted hydrogen (a.w. hofmann), cs2 + 2nh3 -> nh2.css.nh4 -> h2s + nh4cns. carbon bisulphide combines with primary amines to form alkyl dithiocarbamates, which when heated lose sulphuretted hydrogen and leave a residue of a dialkyl thio-urea, cs2+2r.nh2 -> r.nh.css.nh3r -> cs(nhr)2 + h2s; or if the aqueous solution of the dithiocarbamate be boiled with mercuric chloride or silver nitrate solution, a mustard oil (q.v.) is formed, r.nh.css.nh3r + hgcl2 -> hg(r.nh.css)2 -> 2rncs + hgs + h2s. carbon bisulphide is used as a solvent for caoutchouc, for extracting essential oils, as a germicide, and as an insecticide. _carbon monosulphide_, cs, is formed when a silent electric discharge is passed through a mixture of carbon bisulphide vapour and hydrogen or carbon monoxide (s.m. losanitsch and m.z. jovitschitsch, _ber.,_ 1897, 30. p. 135).