Basic disazo compounds containing sulphonic acid groups

A compound of formula I ##STR39## which is in an internal and/or external salt form, in which each of R.sub.1 to R.sub.4 is independently hydrogen, halogen, hydroxy, C.sub.1-4 alkyl, C.sub.1-4 alkoxy, --NHCOC.sub.1-4 alkyl or--NHCONH.sub.2,

• each of X.sub.1 to X.sub.4 is independently an aliphatic, cycloaliphatic or heterocyclic amino group containing at least two nitrogen atoms, with the proviso that each of these amino groups bears a protonatable nitrogen atom or quaternary ammonium ion, and at least one of these amino groups bears a primary amino group, and
• X.sub.5 is an aliphatic, cycloaliphatic or heterocyclic amino group containing at least two nitrogen atoms one of which is a protonatable nitrogen atom or quaternary ammonium ion, or an aromatic diamino group of which the terminal amino group is substituted by ##STR40## in which each X.sub.6 and X.sub.7 is independently an aliphatic, cycloaliphatic or heterocyclic amino group which contains at least two nitrogen atoms one of which is a protonatable nitrogen atom or a quaternary ammonium ion, with the proviso that the sum of the protonatable amino groups and quaternary ammonium groups present in X.sub.1 to X.sub.5 exceeds the number of the sulpho groups by at least one and further with the proviso that at least two of X.sub.1 to X.sub.4 contain a primary amino group.