Thermodynamic Parameters of Pr(III), Nd(III) and Sm(III) Chelates with Glutamic Acid

Department of Chemistry, Bipin Bihari College, Shansi-284 001 Manuscript received 30 August 1976, revised 30 March 1977, accepted 3 October 1977. The thermodynamic parameters of Pr(III), Nd(III) and Sm(III) chelates with glutamic acid were determined potentiometrically in aqueous solution at 30±0.1° and 40±0.1° in an ionic strength of 0.1 M KCI. The stability constant (logk), change in free energy (∆G), enthalpy (∆H) and entropy (∆S) for the complexes are reported. The increase in the values of stability constants of rare-earth metal ions with increase in atomic number are explained on the basis of lanthanide contraction.