The heat liberated by isothermal compression permits the determination of the thermodynamic properties of liquid water−heat capacity, compressibility, and expansivity. The results, as a function of pressure and temperature, have been extrapolated as far down as −40 °C. They confirm the existing data in the region of the supercooled liquid and also the existence of a divergence of the measured properties. This could be explained as a lambda transition occuring at −45 °C on isobars p = 0. The abnormal heat capacity which characterizes this transition is well described as a function of the temperature by a formula with critical coefficients as already suggested by others.

Expansivity and compressibility measurements have been made for toluene in the temperature range 200-450 K up to 4 kbar. The experiments were performed by a modified piezothermal technique bringing out a self-consistent set of data for these quantities. An anomaly is observed in the behavior of the heat capacities at low temperature in the high-density region. This has been interpreted as a progressive conversion from one type of molecular motion to another as volume increases. The qualitative aspects of this phenomenon are discussed.

The expansivity of liquid CO2 and of n-butane is determined as a function of pressure up to 4 kbar, from the melting temperatures up to the critical temperatures. The experimental method is piezothermal. The set of data is processed through a fit with a multipoint Padé approximant using an algorithm due to Werner. This particular technique determines, in its reduced form, the unique rational function relevant to the problem. The expansivity of the whole liquid phase is described in terms of a simple equation with four coefficients which enables calculation of the other thermodynamic properties. The general aspect of the phenomenological equations is discussed in this instance, underlining the particular behavior of the heat capacity as a function of pressure.