Dielectric properties of glycerol in the range 0.1–105Hz, 218–357 K, 0–53 kb

Abstract

The dielectric constant and loss of glycerol has been measured in the range 0.1–105 Hz, 218–357 K, and 0–53 kb. A piston-cylinder apparatus was used for the range 0–25 kb and an anvil apparatus for the range 25–53 kb. The static dielectric constant increases with increasing density at a rate that indicates that ∂ln gµ20/∂ ln ρ, where g is Kirkwood's correlation parameter, µ0 the dipole moment of an isolated molecule, and ρ the density, is –0.2. The dispersion region broadens with increasing pressure, and a high-frequency dispersion can be resolved at the higher pressures and lower temperatures. The frequency of maximum loss ƒm decreases with increasing pressure at an increasing rate, a behaviour which is clearly related to the approach to the glass transition. Isotherms can be fitted to the equation ln ƒm=A–B/(p0–P) where A, B and p0 are constants and p0 is the pressure at which ƒm extrapolates to zero.