SOLUBILITY OF SOME CALCIUM-CARBOXYLIC LIGAND COMPLEXES IN AQUEOUS-SOLUTION

Insoluble species were identified in the systems Ca2+-hemimellitate, C a2+-1,2,3,4-butanetetracarboxylate and Ca2+-citrate, and their solubil ities were determined in aqueous solution at T = 25 degrees C. Values of pK(s0) were obtained for the species CaLH (L = benzene-1,2,3-tricar boxylate or hemimellitate), Ca(2)L (L = 1,2,3,4-butanetetracarboxylate ), CaLH and Ca(3)L(2) (L = citrate), together with their dependence on ionic strength. Solid compounds were also characterized by thermograv imetry. The complex formation in solution for the system Na+- and Ca2-hemimellitate was studied too.