Potentiometric Studies on the Ternary Systems : Rare Earth Metal Ions-Cyclohexanediamine Tetraacetic Acid-Dicarboxylic Acids

Chemical Laboratories, Agra College, Agra Manuscript received 18 February 1978, accepted 27 May 1978 Mixed-ligand complex formation in the systems : M(II)-CDTA-Dicarboxylic acids (H2A) [where M(III)=La(III), Pr(III), Nd(III), Gd(III) or Dy(III) ; CDTA= cyclohexanediamine-tetraacetic acid and Dicarboxylic acids (H2A)=phthalic acid (PHA) or malonic acid (MLA), has been discussed and the formation of 1 : 1 : 1 M(III)-CDTA-PHA/MLA species evidenced. The formation constants (log KMLL) and free energies of formation (∆G°) for the resulting ternary chelates have been evaluated. The relative order of stabilities in terms of metal ions : La(III)MLA has been observed