Vapor pressures of nitric acid and water in the systems HNO3-H2O and HNO3-Th(NO3)4-H2O at 50oC

The equilibrium compositions of the vapor above nitric acid-water, thorium nitrate-water, and nitric acid-thorium nitrate-water mixtures at 50oC have been studied as a function of solution concentration by using a transpiration technique. Nitric acid concentrations were varied from 0 to 20 m and thorium nitrate concentrations from 0 to 2.5 m. Our data for the nitric acid-water system have been combined with literature data to obtain parameters for Scatchard's ion-component model, and these parameters provide a satisfactory description of the system at 50oC over a wide concentration range. The enhancement, at 50oC, of the nitric acid vapor pressure by added thorium nitrate was found to be less than that previously determined at 25oC. The data for the nitric acid-thorium nitrate-water system at 50oC were fitted to a single multiparameter function. (author)