A computer program for the simultaneous determination of kinetic and equilibrium constants in aqueous solutions and suspensions is presented. The input of the program SteadyFit consists of serial experimental data which are obtained from completely mixed flow-through systems at different steady-state conditions. The program includes the algorithm STEADYQL, which was developed earlier for the study of chemical speciation and sensitivity with respect to kinetic parameters in aqueous solutions at steady state. The method is adaptable to laboratory experiments where independent variables (e.g., flow velocity or concentrations of reactants) can be controlled easily within a sufficiently wide range. The approach is illustrated with a simple example based on simulated experimental data. The appropriate selection of the dependent variable to be measured is crucial: the best variable to choose is the most sensitive one with respect to the constants to be determined (in our example it is the free hydrogen ion concentration). It is shown that constants with only minor effects on the measured dependent variable are subject to relatively large inaccuracy, while constants with large effects on the steady-state concentration of the dependent variable can be determined with high precision.
