MERCAPTANS (Thio-

See also:

• ALCOHOLS
• ALCOHOLS, ALDEHYDES AND
• ALCOHOLS, BENZYL ALCOHOL, BUTYL ALCOHOLS, METHYL ALCOHOL

alcohols)  , organic chemical compounds of the type R.SH (R=an alkyl group) . The name is derived from mercurium captans, in allusion to the fact that these compounds react readily with mercuric oxide to form crystalline mercury derivatives . The mercaptans may, be prepared by the action of the alkyl halides on an alcoholic solution of potassium hydrosulphide; by the reduction of the sulpho-chlorides, e.g . C2H5SO2C1 (chlorides of sulphonic acids), by heating the salts of esters of sulphuric acid with potassium hydrosulphide, and by heating the alcohols with phosphorus pentasulphide . They are colourless liquids, which are insoluble in water and possess a characteristic offensive smell . On oxidation by nitric acid they yield sulphonic acids . They combine with aldehydes and ketones, with elimination of water and formation of mercaptals and mercaptols . (See SULPHONAL.) Methyl mercaptan, CHI.SH, is a liquid which boils at 5.8° C . (752 mm.), and forms a crystalline hydrate with water . Ethyl mercaptan, C2H5.SH, is a colourless liquid which boils at 36.2° C . It is used commercially in the preparation of sulphonal (q.v.) . The mercury salt, Hg(SC2Hb)2, crystallizes from alcohol in plates .

When heated with alcohol to 19o° C. it decomposes into mercury and ethyldisulphide .