Contribution of the concept of simple solutions to calculation of the density of ternary and quaternary solutions of thorium(IV) or plutonium(IV) nitrate: An(NO3)(4)/UO2(NO3)(2)/HNO3/H2O

A method is presented for calculating the density of concentrated ternary a nd quaternary mixtures of nitric acid, thorium(IV) nitrate or plutonium(IV) nitrate, and uranyl nitrate. The method is based on the concept of simple solutions and on the known binary data for each of the electrolytes. The de viation between the calculated and measured density values for ternary An(N O3)(4)/HNO3/H2O mixtures was less than 0.3 % for densities of up to 1.797 g .cm(-3) in the case of Pu(NO3)(4). Density predictions for quaternary mixtu res containing uranyl nitrate as the additional electrolyte were also inves tigated; the results show that the density of such mixtures can be predicte d with less than 0.4% error, even at very high concentrations (1.836 g.cm(- 3)) in the case of Pu(NO3)(4).