PVT Properties of Water. III. Virial Coefficients of D2O in the Range 150°–500°C

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Abstract
The equation of state of D2O has been determined at 25° intervals from 150° to 500°C by the methods used previously for H2O in which no measurements of the vapor volume are required. The conditions reproduced those used for H2O, and the results were analyzed to give the differences in the second virial coefficient of D2O and H2O to maximum precision. The enthalpy and energy of dimerization is about 20 cal mole−1 lower for D2O than for H2O, and the entropy of dimerization is about 0.03 cal deg−1·mole−1 lower. These values agree qualitatively with other related evidence; a quantitative comparison is not possible at present because the large effects of the quantization of the intermolecular motions, particularly rotational and vibrational, are not known well enough.