Relative Permittivity of Dimethylsulfoxide and N , N -Dimethylformamide at Temperatures from (278 to 328) K and Pressures from (0.1 to 5) MPa

Relative permittivities (ε r ) have been measured at two frequencies with an expanded ( k = 2) uncertainty of 0.1 using a re-entrant radio frequency resonator in the pressure range (0.1 to 5) MPa at temperatures from (278 to 328) K for N, N -dimethylformamide (DMF) and (293 to 328) K for dimethylsulfoxide (DMSO). At 298.15 K and 0.1 MPa, the assessed literature averages of 38.4 ± 1.8 and 47.3 ± 1.8 for DMF and DMSO, respectively, are consistent with the values of 37.2 ± 0.1 and 46.0 ± 0.1 determined in this work. Possible sources of uncertainty are discussed. An empirical description of ε r ( p, T ) is given that can be used to calculate the temperature and pressure derivatives of ε r . Kirkwood g factors calculated using the present data show only minimal dipole−dipole correlations for both DMF and DMSO.