The heat capacity at constant volume C
V
of pure water has been measured in the temperature range
from 412 K to 693 K at 13 isochores between 250 kg·m-3 and 925 kg·m-3. Measurements cover the
critical region and coexistence curve. Measurements have been made in both the one- and two-phase
regions near the phase transition points. The measurements were made in a high-temperature, high-pressure adiabatic nearly constant-volume calorimeter. The uncertainty of the heat capacity measurements is estimated to be within ±2.5%. Liquid and vapor one- (
) and two-phase (
) heat
capacities, temperatures (T
S), and densities (ρS) at saturation were obtained by the method of quasi-static thermograms. The parameters (c, T*,V
*) of the simplified-perturbed-hard-chain-theory (SPHCT)
equation of state have been optimized to allow calculations of heat capacities for water in the vapor and
liquid phases. The relative average deviations for H2O were within about ±4.5%, except in the critical
region where differences reached 15−20% or more. The two-phase heat capacity data C
V
2 were used to
evaluate the second temperature derivatives of the vapor pressure and chemical potential. Values of the
vapor pressure of water were calculated from C
V
2 measurements using critical pressure and the
temperature derivative of the saturation pressure at the critical point.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.