Bismarck brown

…more of the diamine gives Bismark brown, a major component in the first successful disazo dye—i.e., a dye with two azo groups. In 1884 a conjugated disazo dye, Congo red, made by coupling 4-sulfo-1-naphthylamine with bisdiazotized benzidine, was found to dye cotton by simple immersion of the fabric in a…