Dielectric properties of glycerol in the range 0.1–105 Hz, 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 ƒ_m 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 ƒ_m=A–B/(p₀–P) where A, B and p₀ are constants and p₀ is the pressure at which ƒ_m extrapolates to zero.