Abstract

A recent suggestion by Gustavson’ that the basic groups may become bound to condensed vegetable tannins by irreversible forces stronger than hydrogen bonds such as a form of quinone tannage, and that these bonds are the main factor in elevating the shrink temperature in vegetable tannage, is examined in relation to the evidence for and against this interesting concept. It would appear that the weight of evidence is against this suggestion, and the data given by Gustavson are shown to be capable of alternative explanations. This does not preclude the possibility of a quinone type of tannage under abnormal conditions. Nor does i deny the probability that the charged basic groups of the protein are reversibly associated with con veniently situated opposite residual charges on the large tannin molecule. The tannin molecule is bound to the protein at many points by hydrogen bonds, the interchain bridging effect being responsible for shrink temperature elevation. There appears to be general agreement that vegetable tannins and syntans containing an acidic carboxyl or suiphonic group will form “salt” links to the basic groups of the collagen.