摘要:
Leather dyeing agents, which can be obtained by concentrating, by means of a membrane separation process, the mother liquors, which are produced in the salting-out process in the preparation of organic dyestuffs which are water-soluble or which contain groups imparting water-solubility, the mother liquors having an extinction in the absorption maximum which is .gtoreq.500, with a layer thickness of 10 cm, and by drying the concentrate, if appropriate.