Thermodynamic properties of mixtures of H[sub 2]O and D[sub 2]O in the critical region.

An accurate equation of state is presented for the thermodynamic properties of mixtures of H[sub 2]O and D[sub 2]O in the critical region. The equation incorporates a crossover from fluctuation-induced singular behavior near the locus of vapor–liquid critical points to regular behavior outside the critical region. It is a generalization of a crossover equation-of-state previously developed for pure H[sub 2]O and pure D[sub 2]O extended to the mixtures on the basis of the principle of isomorphism of critical behavior. The equation represents the thermodynamic properties of mixtures of H[sub 2]O and D[sub 2]O in the same range of temperatures and densities as for the pure components. A comparison is made with available experimental data for the pressure, for the isochoric heat capacity, for the enthalpy of mixing, and for the isotope fraction ratio of mixtures of H[sub 2]O and D[sub 2]O. An analysis is presented of the near-critical behavior of various thermodynamic properties, such as the isobaric heat capacity, the partial molar volumes, Henry’s constant, and the vapor–liquid distribution ratio (K factor). © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]