FORMATION AND STABILITY OF MIXED PROTON-DIETHANOLAMINE-CARBOXYLIC LIGAND COMPLEXES IN AQUEOUS-SOLUTION

The formation and stability of mixed diethanolamine-carboxylic ligand complexes has been potentiometrically, in aqueous solution, at T = 25 degrees C. The protonated amine forms three species, (dea)LH, (dea)LH2 and (dea)(2)LH2 [(dea) = diethanolamine, L = carboxylic ligand] with malonate, malate and tartrate, and six species with butanetetracarboxy late, (dea)LH, (dea)LH2, (dea)LH3, (dea)LH4, (dea)(2)LH2 and (dea)(2)L H3. The stability of these species is comparable with that of the alka li metal complexes of carboxylic ligands. The formation constants can be predicted, by a simple linear relationship, as a function of the ch arges involved in the complexation reaction.