Crosslink nature in Cr(III)-polyacrylamide gels

The equilibrium constants of various candidates for the crosslinking reacti on between chromium(III) and partly hydrolysed polyacrylamide have been cal culated. For this purpose use has been made of a) the crosslinking index in gels to calculate the concentration of crosslinks, b) pH-dependent concent rations of various hydrolysis products of Cr3+ ions and c) pH-dependent con centration of free carboxylic acid anions. The conclusion is that the cross links consist of two carboxylic acid anions coordinated with the dimerisati on product of the Cr3+ ions.