Pressures on the Critical Isochore ofHe4

Abstract

Measurements are reported of ${\left(\frac{\partial P}{\partial T}\right)}_{{\rho }_c}$ on the critical isochore of ${\mathrm{He}}^4$ very close to the critical temperature. The measurements are well represented by an equation of the form ${\left(\frac{\partial P}{\partial T}\right)}_{{\rho }_c}=D+B^{*}t+A^{*}t\ln \mathrm{}\left(t\right)\mathrm{}$, where $t=\frac{(T-T_c)}{T_c}$ in the interval $-0.016<t<\mathrm{}0.013\mathrm{}$. They are used with Moldover's heat-capacity data to calculate ${\left(\frac{\partial \mu }{\partial T}\right)}_{{\rho }_c}$, which is found to be a linear function of temperature in the same temperature interval and to be analytic at the critical point. A comparison of the 1958 ${\mathrm{He}}^4$ vapor-pressure temperature scale ($T_{58}$) with the NBS Provisional Scale 2-20 K (1965) indicates that $T_{58}$ is a very unsuitable temperature scale for ${\mathrm{He}}^4$ critical-point work.