  We introduce an experimental method of assessing the vibrational and
configurational components of the excess entropy of a liquid over crystal,
based on a joined investigation of dynamic and thermodynamic properties as a
function of temperature and pressure. We analyze light scattering, dielectric,
calorimetric and dilatometric measurements of three prototype glass formers,
orthoterphenyl, salol, and glycerol. In all cases we find that about 70% of the
excess entropy is configurational in nature.
