The Static Dielectric Constant of Liquid Water Between 274 and 418 K Near the Saturated Vapor Pressure

The complex dielectric constant (relative electric permittivity) of liquid water was redetermined in the temperature range 0°C<;t<145°C at pressures less than 440 kPa. In this work, _r was deduced from measurements of the resonant frequencies f of a novel, re-entrant, two-mode, radio-frequency resonator. The frequencies ranged from 23 to 84 MHz and were well within the low-frequency limit for because (2f_max)²<5×10^–5 where _max=1.8×10^–11 s is the maximum relaxation time of water under the conditions studied. The data for for two water samples differing in conductivity by a factor of 3.6 and for the two resonant modes differing in frequency by a factor of 2.6 were simultaneously fit by the polynomial function (t)=87.9144–0.404399t+9.58726×10^–4t²–1.32802×10^–6t³ with a remarkably small residual standard deviation of 0.0055. The present data are consistent with previously published data; however, they are more precise and internally consistent. The present apparatus was also tested with cyclohexane and yielded the values (t)=2.0551–0.00156t for 20°C<t<30°C, in excellent agreement with previously published values.