Abstract

A study has been made of the fixation and tanning action of zirconium compounds on chromium tanned pelt. Zirconyl sulphate does not interfere with effective chromium tannage and therefore can have little affinity for the carboxyl groups of the protein, but it displaces chromium complexes loosely held by auxiliary valencies without reducing the shrinkage temperature of the chromium leather. Zirconyl chloride, although only fixed to a very limited extent, apparently forms co-ordination compounds with the protein carboxyl groups, disrupting the chromium tannage because there is an over-all loss of hydrothermal stability. Thus it is thought that the mechanism of the reaction of basic zirconium sulphate (which is the only zirconium salt of commercial interest) with collagen is multipoint attachment of the tanning material by residual valency forces, although charge effects with basic groups may be supplementary.