Thermodynamic Properties of Actinide Complexes. Part 1. Uranyl(VI) Monocarboxylate Complexes.

The changes in free energy, enthalpy and entropy for the formation of uranyl(Vl)-monochloroacetate, -\uf062-chloropropionate and -acetate have been determined at 25 \ub0C and in aqueous perchlorate medium of ionic strength 1.00 M. The changes in free energy were obtained from stability constants determined potentiometrically, the corresponding enthalpy changes by direct calorimetric titrations. All the complexes are found to be stabilized by a large gain of entropy, while the enthalpy term, excepting the third step in the uranyl(Vl)-acetate system, opposes the complex formation