INDULINES  , a

series of dyestuffs of blue, bluish-red or black shades, formed by the interaction of para-amino azo compounds with primary monamines in the presence of a small quantity of a mineral acid . They were first discovered in 1863 (English patent 3307) by J . Dale and H . Caro, and since then have been examined by many chemists (see O . N . Witt, Ber., 1884, 17, p . 74; O . Fischer and E . Hepp, Ann., 1890, 256, pp . 233 et seq.; F . Kehrmann, Bet., 1891, 24, pp . 584, 2167 et seq.) .

They are derivatives of the eurhodines (aminophenazines, aminonaphthophenazines), and by means of their diazo derivatives can be de-amidated, yielding in this way azonium salts; consequently they may be considered as amidated azonium salts . The first reaction giving a

clue to their constitution was the isolation of the intermediate azophenin by O . Witt (Jour . Chem . Soc., 1883, 43, p . 115), which was proved by Fischer and Hepp to be dianilidoquinone dianil, a similar intermediate compound being found shortly afterwards in the naphthalene series . Azophenin, Ca,H24N4, is prepared by warming quinone dianil with aniline; by melting together quinone, aniline and aniline hydrochloride; or by the action of aniline on para-nitrosophenol or para-nitrosodiphenylamine . The indulines are prepared as mentioned above from aminoazo compounds: NH2•C6H4N2•Celia-I-C6I-ISNH,-> HN : C6H3<N,CoH6> C6H4, (aposafranine) or by condensing oxy- and amido-quinones with phenylated ortho-diamines (F . Kehrmann, Ber., 1895, 28, p . 1714): H0>C6H2H+C6H,NH>C6H4= 2H2O--HO>C6H2<N C6H5 The indulines may be subdivided into the following groups:—(I) benzindulines, derivatives of phenazine; (2) isorosindulines; and (3) rosindulines, both derived from naphthophenazine; and (4) naphthindulines, derived from naphthazine . T NH:C6H3<N;.CaH6> C€H4 NH: C€H3<N,CoH6>CioH6 I . Benzindulines .

II . Isorosindulines . NH: CioH5<N.CeHa>C€H4 NH: CioH5<NC6H6> CioHa The rosindulines and naphthindulines have a strongly basic

character, and their salts possess a marked red colour and fluorescence . Benzinduline (aposafranine), C16H13N3, is a strong base, but cannot be diazotized, unless it be dissolved in concentrated mineral acids . When warmed with aniline it yields anilido-aposafranine, which may also be obtained by the direct oxidation of ortho-aminodiphenylamine . Isorosinduline is obtained from quinone dichlorimide and phenyl-13-naphthylamine; rosinduline from benzeneazo-a-naphthylamine and aniline and naphthinduline from benzeneazo-a-naphthylamine and naphthylamine .