POTENTIOMETRIC STUDY OF THE STABILITY OF EU3+ ACETATE COMPLEXES AS A FUNCTION OF PRESSURE (1-1000 BAR) AT 25°C

Abstract

The stability of europium acetate complexes was examined potentiometrically at 25°C as a function of pressure in the range of 1-1000 bar. The measurements were carried out in an isothermal potentiometric cell with a liquid junction. The cell consisted of a pH glass electrode and an Ag, AgCl (3m KCl) reference electrode. The calibration of the cell on standard solutions has demonstrated that its electromotive force is independent of pressure. Based on pH measurements under various pressures in four acetate solutions with pH from 3 to 4.7 and containing 0.0142m Eu, we determined the standard partial mole volumes and the HKF parameters for the complexes Eu(Ac)2+ and Eu(Ac)+2. The baric dependence of the ΔfG0 of the third complex, Eu(Ac)03, was evaluated from correlations. The stability of all three Eu acetate complexes decreased with pressure: as the pressure was increased from 1 to 1000 bar, the constants of formation of the complexes decreased by factors of 1.5-3 at 25°C and 2-6 at 170°C. © Pleiades Publishing, Inc. 2006.