Rn. Roy et al., Activity coefficients of HCl+GdCl3+H2O system from 5 to 55 degrees C. Application of Pitzer formalism, J SOL CHEM, 29(7), 2000, pp. 619-631
The emf of the cell
Pt, H-2 (g, 1 atm) \ HCl (m(A)), GdCl3 (m(B)) \ AgCl, Ag
without a liquid junction was used to investigate the HCl + GdCl3 + H2O mix
ed electrolyte system. The emf of the cell was measured for HCl + GdCl3 + H
2O solutions at ionic strengths of 0.025, 0.05, 0.1, 0.5, 1.0, 1.5, and 2.0
mol-kg(-1) and at eleven temperatures ranging from 5 to 55 degrees C at 5
degrees C intervals. The mean activity coefficients for HCl in the mixtures
were determined using the Nernst equation. About 793 experimental emf data
points were treated by the Harned equations. Results show that hydrochlori
c acid follows Harned's rule at all ionic strengths, but the quadratic term
is needed for I = 1.5 mol-kg(-1). The ion-interaction treatment of Pitzer
was used to evaluate the results. The binary and ternary mixing parameters
at 25 degrees C were found to be Theta(H,Gd) = 0.07 +/- 0.03 and psi(H,Gd,C
l) = 0.14 +/- 0.03. These values were determined using literature values of
beta((0)), beta((1)). and C-phi for GdCl3 at 25 degrees C and estimates of
the effect of temperature from 5 to 55 degrees C using enthalpy and heat c
apacity data.