Kinetics of series first-order reactions. Analysis of spectrophotometric data by the method of least squares and an ambiguity

Abstract

A least squares method of analyzing spectrophotometric data for a series first-order process, [graphic ommitted], is given for the case where the unknown parameters are k1, k2 and the extinction coefficient of B. Care is needed, since two solutions fit the experimental data equally well. These solutions correspond to a faster formation of a more weakly absorbing intermediate B, and a slower formation of a more strongly absorbing species. Methods of resolving the ambiguity are discussed, and the problem is illustrated with data obtained by the stopped-flow method for the formation and decay of peroxynitrous acid in acidic solutions.