Computer Analysis of Equilibrium Data in Solution. A Method for Computing the Formation Constants of two Mass Balance Systems, from Potentiometric Measurements, Applied to the Hydrolysis of Copper(II)

A computer program for two mass balance systems (in solution) has been written in FORTRAN IV. This program (ES3TM) refines the formation constants and some titration parameters (E0, analytical concentrations) from potentiometric data, using the Marquardt algorithm for the Gauss nonlinear least squares method. The program has been compared with some other programs reported in the literature. In order to test the ES3TM program and to obtain reliable values of formation constants for the species, [Cup(OH)q](2p–q)+, we studied the hydrolysis of copper(II) by pH-metric measurements at 37°C and I=0.15 mol dm–3 (NaNO3). The results of the refinement have been discussed in the light of the characteristics of the ES3TM program and of the reliability of the speciation models on copper(II) hydrolysis reported up to now.