Spectrophotometric Determination of Formation Constants of Various Complexes of a Metal and Establishment of Probable Number of Such Successive Overlapping Complexes Using Kinetic Data

Abstract

Cerium (IV) forms a number of successive overlapping complexes with hypophosphorus acid. Yatsimirskii method is useful for the determination of formation constants of such complexes but fails to establish their probable number. A useful method is evolved by the application of an iterative method using kinetic data. Yatsimirskii method is applied by first assuming six complexes (1 : 1 to 1 : 6). Rate constants (k₁, k₂, k₃ etc.) are then calculated for each of them using kinetic rate equation. Values are found absurd. Whole of the procedure is then repeated by assuming four successive complexes leading to the values of formation constants (K₁, K₂, K₃ and K₄) for 1 : 1 to 1 : 4 complexes. The iterative method is then applied again for the determination of four rate constants. Very satisfactory values of k₁, k₂, k₃, and k₄ conforming to the kinetic data, are obtained, indicating the probable number of complexes to be four and not six.