The Nature of Calcium and Thorium Complexation by Halate Ligands

The thermodynamics of complexation of Th+4 and Ca+2 ions with chlorate, bromate, and iodate ligands were studied using solvent extraction and calorimetric techniques. The measurements were obtained at LOOM (NaClO4) ionic strength and 25[ddot]C. The results are compared to the values for complexation of Eu+3 by the same ligands and are interpreted to reflect outer sphere complexation for the chlorate complexes, an inner sphere complexation for the iodates and mixed behaviour for the bromates.