Direct Black EW
by : Rahul Sharma
1. Direct Black EW
It is trisazo type dye. Prepared by first acidic coupling of H-acid with benzidine tetraazo, second alkaline coupling of the monoazo dye on H-acid part with phenyl diazonium salt and lastly the third acidic coupling of the bisazo diazonium compound thus obtained to m-phenylenediamine as shown in the scheme.
