Determination of Polynuclear Stability Constants of Th4+ with [NaP5W30O110]14-

D. E. Wall* and G.R. Choppin

Department of Chemistry, Florida State University, Tallahassee, Florida 32306-4390 USA


The b101, b201, and b301 stability constants of Th4+ with [NaP5W30O110]14- were determined in 0.10 M NaCl solution at 25 ºC. Determination of log b101 by solvent extraction of tracer 230Th gave a value of 6.18 0.07. The best fit of a curve for a plot of the data of free Th vs. total natural Th spiked with 230Th was used to calculate the polynuclear stability constants for the ML, M2L and M3L complexes. Values of log b101, log b201, and log b301 of 6.10 0.05, 11.4 0.10, and 16.4 0.15, respectively, were calculated. Enthalpies of complexation, determined by calorimetric titration, for DH101, DH201, and DH301, are 22.0 2.4, 22.0 2.4, and 23.4 2.0 kJ mol-1 respectively. The entropies of complexation, DS101, DS201, and DS301, are 191 22, 292 38, and 393 57 JK-1mol-1, respectively.