Energies of the phases of ice at low temperature and pressure relative to ice Ih

The enthalpy of transformation to ice Ic of ice II, IX, V, VI, and VIII that have been recovered at 77 K and ambient pressure, and of the transformation of ice Ic to Ih, has been measured in a heat-flow calorimeter. The enthalpy of transformation of ice Ic to Ih depends on the high-pressure phase used to make the ice Ic. The thermodynamics of the transformation of ice IX, which was made by cooling ice III at 0.3–0.7 K s −1 , to ice III shows that the ice IX was fully orientationally ordered to the precision of the experiments.