A damped non-linear least-squares computer program (DALSFEK) for the evaluation of equilibrium constants from spectrophotometric and potentiometric data

Abstract

A computer program (DALSFEK) has been developed which uses a damped non-linear least-squares iterative method to fit equilibrium constants to spectrophotometric and potentiometric data. The program has been designed in such a way that subroutines that can deal with other types of response variable can easily be added, and the program can utilise several types of observed data simultaneously. An efficient least-squares algorithm due to Marquardt, which combines the method of steepest descent with methods based on the Taylor series in such a way as to exploit the advantages of each, ensures smooth convergence to minimum-variance estimates of the parameters. Facilities are incorporated which allow adjustments to be made to allow for possible sources of systematic errors. The program has been tested on a number of systems and found to be very convenient to use as well as giving satisfactory results.