Determination of fictive binary data for plutonium(IV) nitrate

A method is described for determining binary data for electrolytes from a study of a ternary mixture. The method is based on the concept of thermodynamically simple solutions and on water activity measurements. An application is described in which binary data for plutonium(IV) nitrate are determined from a ternary mixture of Pu(NO3)(4), HNO3 and H2O. This novel application allows the thermodynamic behavior (activity coefficient) to be defined for a fictive solution of plutonium(IV) nitrate in water; the solution is fictive in that it does not correspond to physical reality, given that Pu(IV) is insoluble. The results can be used to calculate the activity coefficient of the electrolyte Pu(NO3)(4) in any type of mixture containing nitric acid and other electrolytes for which the binary data are known.