TERNARY NaCl+LiCl+H2O MIXED ELECTROLYTE SYSTEM: DETERMINATION OF ACTIVITY COEFFICIENTS BASED ON POTENTIOMETRIC METHOD |
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Authors: | Farzad Deyhimi Mojgan Sabzehzari Zohreh Karimzadeh |
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Affiliation: | a Department of Chemistry, Shahid Beheshti University, Evin-Tehran, Iran |
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Abstract: | The mean activity coefficients for NaCl in a ternary electrolyte system were determined by the potentiometric method, at 25°C, using a solvent polymeric (PVC) sodium-selective membrane electrode (Na+ ISE), containing N,N'-dibenzyl-N,N'-diphenyl-1,2-phenylenedioxydiacetamide as ionophore, and combined with an Ag/AgCl electrode. The potentiometric measurements were performed at the same ionic strengths in different series of mixed salt solutions, each characterized by a fixed salt molal ratio r (where r = m1/m2 = 1, 10, 50, 100). The nonideal behavior of the ternary NaCl(m1) + LiCl(m2) + H2O electrolyte system was described based on the Pitzer ion-interaction model for mixed salts over the ionic strength ranging from 0.01 up to about 4 mol/kg. Two- and three-particle Pitzer interaction parameters for a mixed electrolyte system were determined based on potentiometric data, and the critical role of potentiometric selectivity coefficient (K12) of ISE as limiting factor in the potentiometric measurements was analyzed. |
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Keywords: | Activity coefficient Lithium chloride Pitzer equations Sodium chloride Sodium ion-selective electrode |
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