Abstract

A mixture of aquo complexes of chromium(III) is used for tanning. These complexes vary in their nature and reactivity to the protein. The present investigation deals with the understanding of the nature of the chromium(III) complexes present in spent chrome tanning solutions. An ion exchange chromatography technique has been employed for the isolation of the various complexes from fresh and spent tanning solutions. These studies indicated the presence of low affinity species to the extent of 45% of the total chromium in the spent solution. The low affinity chromium (III) complex was characterised by UV—visible spectroscopy, charge per atom, charge per species, degree of polymerisation and hydroxyl per chromium and has been established to be a cyclic tetrapositive tetrameric species with unusual reactivity.