Kinetic Study on the Induced Coordination Reaction of Lanthanum with p-Acetylcarboxylazo

The absorption spectra of p-ACA（p-acetylcarboxylazo）and its complex with lanthanum ionswere determined.The molar ratio of metal to ligand in the complex was estimated to be 1:2.An inductionperiod was found existing in the coordination reaction between La and p-ACA and the effects oftemperature,acidity and ionic strength on the induction period were studied.The reaction mechanism wasdepicted.The rate equation is consistent with the rate law,R=k[La（H2O）63+][H3O+],obtained by kineticmethod.Finally the possible geometric structure of this complex was discussed.