Use of sulfonated polyazo dyes for dyeing leather in brilliant fast red shades

The process for dyeing of leather which comprises the use of a compound of the formula ##STR31## in which R and R.sub.1 independently of one another are hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, unsubstituted or substituted C.sub.2 -C.sub.4 alkanoylamino or substituted or unsubstituted benzoylamino, R.sub.2 is hydrogen or sulfo and X is hydroxy, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 alkylthio, amino, cyclohexylamino, morpholino, 3-carboxy- or 3-carbamoyl-pyridin-1-yl, halogen or substituted or unsubstituted phenylamino or N-C.sub.1 -C.sub.4 alkyl-N-phenylamino.