Estimation of Activities in the Aqueous Solution Systems of HCl-CuCl2 and HCl-FeCl3 Using the Pitzer Method

Abstract

Parameterizations based on the literature activity data have been attempted for the activities of water and the solutes in the aqueous solution systems of HCl–CuCl2 and HCl–FeCl3 at 298 K in terms of the Pitzer theory without explicitly considering complex formation. The single electrolyte parameters for CuCl2 and FeCl3 were determined from the osmotic coefficients for the corresponding single electrolyte solutions. Extra parameters of β(2) were included in the single electrolyte parameters for CuCl2 and FeCl3 to extend the applicable concentration ranges. For the aqueous solution of HCl-CuCl2, two kinds of activity data, namely, the osmotic coefficients measured by the transpiration method and the solubilities of the copper salt, were simultaneously submitted to the weighted linear least-squares analysis to determine the mixed electrolyte parameters. The χ2-test of significance indicated that the Pitzer parameters obtained in this study can reproduce these activity data with no statistically significant error. As a result, the mean activity coefficients of the solutes in this solution system calculated by the parameters obtained in this study are in good agreement with those calculated by the McKay-Perring method. For the aqueous solution of HCl-FeCl3, the osmotic coefficients by the transpiration method were submitted to the weighted linear least-squares analysis; however, the χ2-test of significance indicated that the Pitzer parameters obtained in this study cannot reproduce the activity data without statistically significant error. As a result, the agreement is unsatisfactory between the mean activity coefficients of the solutes in this solution system calculated by the parameters obtained in this study and those by the McKay-Perring method. © 1992, The Japan Institute of Metals. All rights reserved.