Electromotive Force Method Of Licl / Of Cscl In H <sub> 2 </ Sub> O Or Roh-h <sub> 2 </ Sub> O (r = Me, Et) In The Mixed Solvent Thermodynamic Properties

The study of Lithium, Cesium in aqueous or aqueous-organic mixed solvents could enrich the thermodynamic data of alkali chloride. This work is useful for salt lake brine systems containing Lithium and Cesium and to make utilization of the resources in salt lake. The electromotive force measurement is widely used to determine the activity coefficient of electrolytes in solution in comparison with other techniques. In this work, we had carried out the investigation of LiCl + MeOH/EtOH + H₂O, CsCl + Cs₂SO₄ + H₂O, CsCl + Cs₂SO₄ + EtOH + H₂O systems using EMF measurement.(1) The cell arrangement in this work was a galvanic cell without liquid junction made by the pair of lithium ion-selective electrode and Ag|AgCl electrode:Li-ISE | LiCl(m), alcohol(Y), water(100-Y) | Ag|AgClThe above cell was employed to determine the EMF values E of LiCl in mixed solvent at 298.15 K (the ionic strength range from 0.0041 to 1.5293 mol/kg). The activity coefficients of LiCl in MeOH/EtOH-H₂O mixed solvents were calculated by the experiment data, osmotic coefficient and the standard energy of transference have also been calculated in the same molality range. The experimental data were fitted by the Pitzer model and Pitzer-Simonson-Clegg model. The values of E⁰ and corresponding parameters required in the Pitzer model and Pitzer-Simonson-Clegg model have been evaluated for this system. It was found that the Pitzer model was as well as Pitzer-Simonson-Clegg model, and both models are satisfactory for our work.(2) The cell arrangement in this work was established by the pair of cesium ion-selective electrode and AglAgCl electrode:Cs-ISE | CsCl (m_A0) | Ag|AgClCs-ISE | CsCl (m_A), Cs₂SO₄(m_B) | Ag|AgClThe electromotive forces of the above galvanic cells were measured at 298.15 K. (the ionic strength range from 0.0009 to 1.0445 mol/kg). The experimental data were interpreted using Harned's rule and the Pitzer model. The corresponding parameters required in the Pitzer model have been evaluated for these two systems. Osmotic coefficients of these two systems and activity coefficients of the second salt Cs₂SO₄were also calculated in the same range. The standard deviations between the calculated and experimental data were reported, which indicated the Pitzer ion-interaction model can describe the thermodynamic properties for these systems.