Pressure dependence of the thermodynamical Grüneisen parameter of fluids

Temperature changes associated with adiabatic pressure changes have been measured for water, mercury, pentane, isopentane, ethanol, methanol, and ether. For the first four fluids mentioned, the pressure dependence of the adiabatic bulk modulus, Ks, is known from ultrasonic measurements, and the Grüneisen parameter can be calculated using the thermodynamic relationship γth= (Ks/T)(ℓT/ℓP)s. For all fluids except water a large decrease of ΔT/ΔP with pressure is observed and the ΔT/ΔP curves converge at about 2.5 °C/kbar before freezing occurs. A considerable increase of γth with pressure is observed.