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.