Isochoric heat capacity of heavy water at subcritical and supercritical conditions

The heat capacity of heavy water was measured in the temperature range from 294 to 746 K and at densities between 52 and 1105 kg.m(-3) using a high-te mperature, high-pressure adiabatic calorimeter. The measurements were perfo rmed at 14 liquid and 9 vapor densities between 52 and 1105 kg.m(-3). Uncer tainties of the measurements are estimated to be within 3% for vapor isocho res and 1.5% for the liquid isochores. In the region of the immediate vicin ity of the critical point (0.97 less than or equal to T/T-c less than or eq ual to 1.03 and 0.75 less than or equal to rho/rho(c) less than or equal to 1.25), the uncertainty is 4.5%. The original C-V data were corrected and c onverted to the new ITS-90 temperature scale. A parametric crossover equati on of state was used to represent the isochoric heat capacity measurements of heavy water in the extended critical region, 0.8 less than or equal to T /T-c less than or equal to 1.5 and 0.35 less than or equal to rho/rho(c) le ss than or equal to 1.65. The liquid and vapor one- and two-phase isochoric heat capacities, temperatures, and saturation densities were extracted fro m experimental data for each measured isochore. Most of the experimental da ta are compared with the Hill equation of state, and the overall statistics of deviations between experimental data and the equation of state are give n.