Density, Viscosity, Speed of Sound, and Refractive Index of Nitric Acid–Water System

Different concentrations of nitric acid are routinely used in various steps of the nuclear fuel cycle in both the front and back ends. The physical properties of nitric acid–water mixtures are essential to design solvent extraction equipment used in nuclear fuel cycle. However, apart from density, comprehensive information about other physical properties (e.g., viscosity) is lacking. This work addresses this gap area. Four different physical propertiesdensity, viscosity, speed of sound, and refractive indexof different concentrations of nitric acid in water (w f = 0–0.490) are reported for different temperatures (5–50 °C). Empirical correlations have been developed to represent the data set generated. The effect of nitric acid concentration on the speed of sound is really interesting. At lower temperatures, the speed of sound increases nonlinearly with an increase in concentration, while at higher temperatures, the trend is reversed. There is an inflection point at around w f = 0.275 nitric acid concentration where the plots tend to converge. Such insights are reported for the first time. Derived thermoacoustic variables (isentropic compressibility, intermolecular free length, acoustic impedance, molar speed of sound, and molar compressibility) for a nitric acid–water mixture have also been computed and reported, once again for the first time. Furthermore, a comparison of all physical properties of fresh and equilibrated nitric acid/water mixtures (with 35.73 wt % TBP in dodecane) is also reported.