Static dielectric constants for liquid water from 300 K to 350 K at pressures to 13 MPa using a new radio-frequency resonator

A stainless steel reentrant cavity with primary resonances at three frequen cies has been constructed and used to make dielectric constant measurements on liquid water between 300 K and 350 K, at pressures to 13 MPa. At; the f requencies of this study (25 MHz to 250 MHz), there is no evidence of frequ ency dependence in the water data. Three methods have been used to convert resonant frequencies to dielectric constants. Using a lumped-parameter mode l recommended recently by NIST investigators, the dielectric constants from the current work agree within 0.1 with the best data available from other recent investigations. Temperature and pressure derivatives of the dielectr ic constant are nearly identical using all three methods, and they are foun d to be in reasonable but not perfect agreement with the best available cor relation of previous results. A waveguide model approach resulted in dielec tric constants about 0.3 higher than accepted values, likely due to uncerta inties in geometry and materials properties. A second lumped-parameter appr oach also failed, likely due to its dependence on measured resonant frequen cy half widths with water occupying the cavity.