Thermodynamics of Extraction of Nitric Acid by Tri-n-Butyl Phosphate—Hydrocarbon Diluent Solutions: III. Comparison of Literature Data

Some of the published data on the extraction of nitric acid from aqueous solutions, containing ≦5 M acid, by tributyl phosphate-hydrocarbon diluent solutions were tested for their agreement with a mathematical description presented in Part 1. In all cases the agreement of the literature data with this description ranged from adequate to very good, thereby adding support to the interpretation of the parameters of the equation in terms of the equilibrium constant, , for the extraction reaction and the two activity coefficients y′_T and . The form of the mathematics suggests that TBP and TBP·H₂O are indistinguishable in their reaction with HNO₃ and that y′_T is an approximate mean molar activity coefficient of these two in the water-saturated system; similarly, is an approximate mean molar activity coefficient of the two species TBP·HNO₃ and TBP·HNO₃H₂O. The quantity has a value of ∼1.5 in molar units for diluent-free TBP; its extrapolated value in the pure diluent Amsco 125-82, or odorless kerosene, is ∼0.23, while its value in n-hexane is ∼0.27.