Thermodynamic study of the ternary aqueous mixed electrolyte system [(1-y)MgCl2 + yKCl] by electromotive force measurements

The activity coefficients for magnesium chloride in the MgCl2 + KCl + H2O ternary system were determined from electromotive force measurements as a function of total ionic strength and composition of the mixture. In this work, emf measurements were performed on the galvanic cell without liquid junction of the type: Ag|AgCl|MgCl2 (m(1)), KCl (m(2)), H2O|Mg-ISE, at the temperature 298K and over total ionic-strengths from 0.015 to 6 mol kg(-1) for different series of salt molal ratios. The sol-gel-based magnesium ion selective electrode (SG-ISE) and Ag/AgCl electrode used in this work were prepared in our laboratory. The Pitzer model was used for the experimental results correlation of activity coefficients. The unknown Pitzer mixing interaction parameters were evaluated (theta(MgK) = 0.1249, psi(MgKCl) = -0.0572). Then, these parameters were used to predict the thermodynamic properties for the systems under investigation as a function of total ionic strength.