Mean Activity Coefficients of KCl in KCl + SrCl₂ + H₂O Ternary System at 288.15 K Determined by EMF Method

In this work, the studies of thermodynamic mean activity coefficients of KCl in the KCl-SrCl₂-H₂O ternary system have been made. A cell without liquid junction battery cell, K-ISE|KCl(m_A), SrCl₂(m_B)|Cl-ISE, was used to study the activity coefficients in this mixed system KCl-SrCl₂-H₂O at 288.15 K by the electromotive force method. The total ionic strengths ranges are 0.0100-1.0000 mol·kg^-1 with different ionic strength fractions y_b of SrCl₂, that is, y_b = (0, 0.2, 0.4, 0.6, and 0.8). The results show that the K-ISE and Cl-ISE have a good Nernst response. Accordingly, the electromotive forces of the mixed system were measured by using the ion selective electrode listed above, and the mean activity coefficients are also determined with Nernst equation. Using the activity coefficient data, the mixed ion interaction parameters θ_K,Sr and ψ_K,Sr,Cl of Pitzer equations at 288.15 K were fitted by Matlab with linear regression method, respectively. Furthermore, those parameters were applied to calculate the values of the mean activity coefficients of SrCl₂. Finally, the osmotic coefficients, water activity, and the excess Gibbs free energy of this system were evaluated by Pitzer's equations.