ION-SELECTIVE ELECTRODE MEASUREMENTS FOR THE DETERMINATION OF FORMATION-CONSTANTS OF ALKALI AND ALKALINE-EARTH METALS WITH LOW-MOLECULAR-WEIGHT LIGANDS

Formation constants of acetate, hydrogencarbonate, malonate, citrate a nd 1,2,3-propanetricarboxylate complexes with Na+, K+ and Ca2+ were de termined potentiometrically using sodium, potassium and calcium select ive electrodes, at 25 degrees C and at different ionic strengths, in t he range 0<1 less than or equal to 1 M. Formation constants obtained b y ion-selective electrode (ISE) measurements were compared with those obtained by different techniques. It has been found that the use of IS Es gives reliable results in the study of weak complexes, also under n on-constant ionic strength conditions.