Measurement of(∂P∂T)Vand Related Properties in Solidified Gases. I. SolidHe4

A very sensitive strain gauge that is able to detect pressure changes of 2×${10}^{-5\mathrm{}}$ bar inside a small container filled with solidified helium is described. Measurements of the variation of pressure with temperature along several isochores, both in the hcp and in the bcc phase of ${\mathrm{He}}^4$, are reported. From these data, the equation of state at $T=0\mathrm{}$ °K is obtained, leading to the compressibility coefficient $k_T$ and the change in internal energy as a function of volume. The temperature variation of ${\mathrm{k}}_T$ is then obtained at several molar volumes and compared with results from other experiments. The quantity ${\left(\frac{\partial P}{\partial T}\right)}_V$ is tabulated and its temperature variation is discussed. Combination of ${\left(\frac{\partial P}{\partial T}\right)}_V$ data with those of others for the specific heat gives values of the Grüneisen coefficient, which is shown to be volume- and temperature-dependent.