Abstract: In this paper are recommended the values of partical molar volumes of uranyl nitrate and nitric acid in aqueous phase and organic phase, and the change of phase volume was correlated as a function of the solute concentrations. Thus the relations between densities of the solution and concentrations of uranyl nitrate and nitric acid are provided for. The difference between the calculated and experimental values of densities for 95.4% is within±0.020 and±0.017 for the aqueous phase and organic phase respectively. Using the values of partical molar volume changes of volume can be corrected in the course of the extraction process.