Comparison of pressures at 300 K and liquid helium temperatures using a clamp-type bomb

Abstract

A series of measurements in a clamp‐type bomb which relates the pressure at 300 K to the pressure at liquid helium temperatures is described. Below a minimum applied pressure P (300 K), the pressure falls to zero at low temperatures, in agreement with previous observations. Above this pressure, the pressure is found to be a linearly decreasing function of P (300 K). Differential thermal analysis results are given which indicate crystallization rather than a glass transformation for the pressure transmitting medium, a 1:1 mixture of kerosene and mineral oil. A calculation based on known thermodynamic properties of similar organic materials indicates that the observed pressure change is basically due to the pressure dependence of the thermal expansion of the organic fluid mixture.