Heat capacity of water at extremes of supercooling and superheating

Low-temperature heat capacities for water and D₂O have been remeasured with sample preparation and data analysis procedures different from those used in the original studies of this anomalous region. Self-consistent results have been obtained with reproducibilities of 1%. Comparisons are made with the behavior in the superheated region at 1-atm pressure calculated from a refined equation of state by Haar et al. It appears that the kinetic metastability limit of the liquid (nucleation terminated) at both hot and cold extremes may be reached at the same value of the liquid heat capacity.