XANTHIC

ACID (xanthogenic acid)  , C2H5O•CS•SH, an organic acid named from the Greek EavBor, yellow, in allusion to the bright yellow colour of its copper salt . The salts of this acid are formed by the action of carbon bisulphide on the alcoholates, or on alcoholic solutions of the caustic alkalis . They react with the alkyl iodides to form dialkyl esters of the dithio-carbonic acid, which readily decompose into mercaptans and thiocarbamic esters on treatment with ammonia: C2H5O•CS•SR1+NH3=C2H5O•CS•NH2+R1•SH; with the alkali alcoholates they give salts of the alkyl thiocarbonic acids: C2H5O•CS•SR +CH3OK+H2O= CH3O•CO•SK+C2H5OH+R•SH . Ethyl xanthic at-id, C2H5O•CS•SH, is obtained by the action of dilute sulphuric acid on the potassium salt at o° C . (Zeise, Bern . Jahresb., 3, p . 83) . It is a colourless oil which is very unstable, decomposi at 25° C. into carbon bisulphideand alcohol . The potassium salt crystallizes in colourless needles and is formed by shaking carbon bisulphide with a solution of caustic potash in absolute alcohol . On the addition of cupric sulphate to its aqueous solution it yields a yellow precipitate of cupric xanthate . Potassium xanthate is used in indigo printing and also as an antidote for phylloxera . Tschugaeff (Ber., 1899, 32, p .

3332) has used the xanthic ester formation for the preparation of various

terpenes, the methyl ester when distilled under slightly diminished pressure decomposing, in the sense of the equation, C„H2n_1.O.CS•SCH3= C„H2„_2+COS+CH3SH . According to the author molecular change in the hydrocarbon is prevented, since no acid agent is used .