On the low frequency loss peak in the dielectric spectrum of glycerol

We measured dielectric spectra of glycerol at pressures exceeding 1 GPa in order to examine the slow Debye-like peak. This peak is not a relaxation process, but its frequency is consistent with an origin in dielectric discontinuities due to impurities. These heterogeneities have a non-negligible bulk modulus and are identified as volatile, relatively non-polar liquid contaminants. Although this slow peak is often found in the dielectric spectra of polyalcohols, it is not an intrinsic feature thereof, unlike the ostensibly similar relaxation peak in monoalcohols.