A critical review on the stability constants of the fluoride complexes of actinides in aqueous solution and their correlation with fundamental properties of the ions

Literature data on the stability constants of the fluoride complexes of the actinides in different oxidation states have been compiled. In order to ha ve a reasonable inter-comparison, the stability constant (beta(1)) values o btained in diverse ionic strength media are converted to so called thermody namic stability constants, beta(1)(0) using the DAVIES equation (a modifica tion of Debye-Huckel equation). A correlation of the beta(1)(0) values with the fundamental properties of the actinide ions using various models avail able in the literature has been attempted. Using the values of ionic radii and best available values of the stability constants of a large number of m etal ions from recent compilations a comparative study of the various model s or relations available in the literature has been tried. For metal ions i n general, the semi-empirical relation recently developed by BROWN, SYLVA a nd ELLIS (BSE equation) gives the best correlation. In an attempt to accomm odate the unusual trend in the stability constants of the tetravalent actin ides a modification in a parameter of the BSE equation has been proposed. G ood agreement between the theoretically calculated and experimentally deter mined values for actinides in different oxidation states is obtained in mos t of the cases. Further improvements in theoretical relation as well as exp erimental data are required for better correlation.