Activity coefficients for trichloroacetic acid (HTCA) at 25° C from emf measurements of the mixed system HCl + HTCA + H2O

Abstract

Activity coefficient values for trichloroacetic acid (HTCA) at different acid concentrations are determined from a study of its aqueous mixtures with HCl. These values are obtained by fitting the emf measurements of the cell: glass¦HCl (mA) HTCA (mB), AgCl¦Ag, to the Pitzer equations. The mixed system NaCl+NaTCA is also studied to determine the value of the mixing parameter θcl-TCA, needed for substitution in the Pitzer equations. The γ± values are compared with those obtained in previous work from this laboratory (M.A. Esteso et al., J. Electroanal. Chem., 230 (1987) 77), in which the cell used to obtain these values included an uncancelled liquid junction potential, ΔEj, so that they were only apparent values. Finally, an estimation of this liquid junction potential is obtained by combining the apparent values with those calculated in this paper. The potentials thus obtained are compared with those calculated from the Henderson equation.