Determination of the NaFaq association constant for the NaF–NaCl–H2O System at 25–75°C by means of potentiometry

Abstract

Potentiometric measurements are made for the NaF–NaCl–H₂O system at 25, 50, and 75°C using Na⁺- and F^–-sensitive electrodes and a Ag/AgCl reference electrode in both liquid junction and liquid junction free cells. A correction for the liquid junction potential is introduced to the liquid junction cells. The activity coefficients are calculated using the Debya–Hückel equation in the third approximation. The NaF thermodynamic association constants are determined (logK° =–0.375,–0.29, and–0.25) with an error of ±0.1 log units at 25, 50, and 75°C, respectively.