Determination of the Relative Permittivity, ε_r, and Conductance,G, of Methylbenzene at Temperatures between (303 and 393) K and Pressures below 60 MPa with a Concentric Cylinder Capacitor at a Frequency of 1 kHz

Abstract

The real part of the complex relative electric permittivity, ε r (T, p), of liquid methylbenzene has been determined with an estimated expanded relative uncertainty of ± 0.018 % from measurements of the complex capacitance of a concentric cylinder capacitor at temperatures between (293 and 393) K and pressures below 60.6 MPa. The measurements were corrected for the isothermal compressibility of the solid that formed the capacitor. The isothermal compressibility was determined by comparison of measurements of ε r (He, 303 K and 393 K, p) with ab initio results from quantum mechanics. The ε r (T, p) values obtained for methylbenzene were combined with the amount-of-substance density, ρ, which was obtained from the equation of state reported by Lemmon and Span (J. Chem. Eng. Data 2006, 51, 785−850), to calculate the molar polarizability, P, that was fit with an expanded (k = 2) relative uncertainty of ± 0.03 % by three parameters. The ε r (T, p) reported by Kandil et al. (J. Chem. Eng. Data 2008, 53, 1056−1065) from measurements with a radio frequency re-entrant cavity, a technique with entirely different sources of systematic error, were converted to P•ρ and they differed from 1•10 −3 at T = 290 K to −2.5•10 −3 at T = 406 K (with ⟨P•ρ⟩ ≈ 0.31 giving a relative difference of between 0.3 % and −0.8 %, respectively) at temperatures that overlap ours. At T = 298 K the measurements reported by Mospik (J. Chem. Phys. 1969Phys. , 50, 2559Phys. −2569 at a pressure between (0.1 and 20) MPa when converted to the product P•ρ are within −0.8•10 −3 (a relative difference of about −0.26 %) of our smoothing equation while at T = 273 K, about 20 K below our lowest temperature, the differences for P•ρ are −0.4•10 −3 (a relative difference of about −0.13 %).

Memorial Issue in Honor of Anthony R. H. Goodwin: Preface

“…Studies of relative permittivity were another major theme in Tony's research starting with his measurements on refrigerants 12 and water, 10 the development and use of re-entrant cavity resonators, 13,14 and recent measurements using a concentric cylinder capacitor. 15 The relative permittivity measurements by Marsh on nitroalkanes in various nonpolar solvents compliment the above studies. Accurate vapor pressure measurements were a feature of his early work at University College London under the tutelage of the late Douglas Ambrose, initially with measurements on 2-methylbutane.…”

“…Studies of relative permittivity were another major theme in Tony’s research starting with his measurements on refrigerants and water, the development and use of re-entrant cavity resonators, , and recent measurements using a concentric cylinder capacitor . The relative permittivity measurements by Marsh on nitroalkanes in various nonpolar solvents compliment the above studies.…”

Determination of the Relative Permittivity, εr, of Octane at Temperatures between (303 and 393) K and Pressures below 25 MPa with a Concentric Cylinder Capacitor at a Frequency of 1 kHz

“…The apparatus, which was used without alteration, and experimental procedures, including the method used to fill the capacitor with liquid samples, have been described previously by Shen et al, for the determination of ε r (C 7 H 8 , T , p ) and ε r (C 7 H 16 , T , p ) . In this work, ε r ( T , p ) was determined from measurements of capacitance C (C 8 H 18 , T , p ), using eq , with C ( T , p = 0) from eq of ref and κ T that was obtained by comparing measurements of ε r (He, T , p ) with ab initio value results from quantum mechanics as reported in ref .…”

“…The uncertainties of each of the measured quantities were as stated in refs and and are provided as follows for completeness: (1) the capacitance was measured with a relative standard uncertainty of ± 6·10 –6 with a ratio transformer bridge at a frequency of 1 kHz; (2) the temperature was determined on the International Temperature Scale of 1990 with a nominal 100 Ω platinum resistance thermometer with an expanded uncertainty of ± 0.01 K; and (3) pressures were measured with a resonant quartz transducer with an uncertainty of δ p /MPa = {0.0001·( p /MPa) + 0.022}. The uncertainty arising from items 2 and 3 resulted in a negligible additional uncertainty in the determination of ε r ( T , p ).…”

“…The manufacturer also specified the octane contained a measured mole fraction of water less than 0.0005; this x (H 2 O) is equivalent to the recommended mole fraction solubility of water in octane of 5·10 –4 at T = 298.15 K reported by Mączyński et al that was based on the measurements reported by Polak and Lu . The sample was degassed by vacuum sublimation and dried as specified in ref .…”