Potentiometric studies of some lanthanum carboxylates at constant ionic strength

Abstract

Overall stability constants β_pqr[where p is the number of lanthanum(III) atoms, q is the number of hydrogen ions and r is the number of ligands] have been determined at 25 °C for lanthanum glycollate, malate, maleate and tartrate at an ionic strength (I) of 2.0 mol dm^–3 and for lanthanum malonate at I= 1.0, together with those of the corresponding acids. The technique consisted of e.m.f. measurements to ±0.01 mV of a cell containing glass and silver, silver chloride electrodes and calibration by reference to the acid stability constants. The lanthanum β values were computed by two methods and the answers are discussed in terms of the number of complexes formed with each ligand and the factors which influence the calculations.