The distribution of nitric acid between water and tributyl phosphate ‐ hexane solvents

Abstract

AbstractThe distribution of nitric acid between water and solutions of tributyl phosphate in n‐hexane has been measured over a greater range of acid and tributylphosphate concentrations than have been reported previously.The partitioning of nitric acid between water and tributylphosphate‐hexane solvents has been satisfactorily explained on the basis of the commonly accepted equilibrium complexing reaction, with this modification: The over‐all aqueous‐to‐organic reaction is subdivided into the distribution of uncomplexed nitric acid and an organic phase complexing reaction. This alteration is found necessary to account for the behavior of the partitioning data of dilute acid over the entire tributylphosphate‐hexane range. The residual discrepancy between the theory and the data can be qualitatively attributed either to modest nonideality of the organic phase or to the effect of the varying water content of the solvent on the distribution coefficient of uncomplexed nitric acid.The sparse data on water extraction by tributylphosphate‐hexane solvents are not amenable to the same type of analysis, even though a type of complexing similar to that found for nitric acid has been previously proposed. The interaction between water and tributylphosphate appears to be stronger than that normally attributed to nonideality but weaker than a true chemical complex.