A water-soluble disazo compound of the formula ##STR199## in which B is phenylene unsubstituted or substituted by 1 sulfo group or by 1 methyl group or 1 methoxy group or 1 chlorine atom or 2 methoxy groups or 1 methoxy group and 1 methyl group, and the two formula moieties B are identical to or different from one another,
- D is phenylene unsubstituted or substituted by 1 or 2 sulfo groups and the two formula moieties D are identical to or different from one another,
- K represents, as the bivalent radical of a coupling component, the bivalent radical of 1-amino-8-naphthol-4,6-disulfonic acid, and
- Z is .beta.-phosphatoethylsulfonyl, .beta.-sulfatoethylsulfonyl or vinylsulfonyl, or an alkali metal salt thereof.