Theory of volumetric behaviour of hydrous melts. The systems LiNO3–H2O and NH4NO3–H2O

Abstract

An equation for the dependence of the molar volume of a hydrous melt on its molar composition is derived on the basis of the concept of the apparent molar volume of water and from a previous calculation of the distribution of water molecules between sites near ions and sites near water molecules in the melt. The densities of LiNO₃–H₂O and NH₄NO₃–H₂O liquid mixtures have been measured at 333 K over the composition ranges 0.05 < x(LiNO₃) < 0.3 and 0.1 < x(NH₄NO₃) < 0.5, and have been used, together with literature data for the systems NH₄NO₃–H₂O, (Li_0.5K_0.5)NO₃–H₂O, Ca(NO₃)₂–H₂O and Cd(NO₃)₂–H₂O, to test the validity of the derived equation and to calculate the values of the physical parameters involved.