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

The complex dielectric constant (relative electric permittivity) Er = e.ʹ — ie" of liquid water was redetermined in the temperature range 0°C < t< 145°C at pressures less than 440 kPa. In this work, er was deduced from measurements of the resonant frequencies fa 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 eʹ because ( 2 n f xTm a x ) 2<5 x 10- 5 where Tmax= 1.8 x 10-11 s is the maximum relaxation time of water under the conditions studied. The data for cʹ 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 eʹ(t) = 87.9144-0.404399t + 9.58726 x 10-4t2- 1.32802 x 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 iInternally consistent. The present apparatus was also tested with cyclohexane and yielded the values eʹ(t) = 2.0551 —0.00156; for 20°C < t< 30°C, in excellent agreement with previously published values.