High-pressure apparatus for simultaneous adiabatic and isothermal compressibility measurements: Data on argon to 13 kbar

Abstract

A piston‐cylinder apparatus was developed in which ultrasonic waves were transmitted into a high‐pressure sample through the unsupported area of a Bridgman seal. The sound‐wave transmission could be divided so that one portion returned from a fixed reflector in the sample, giving sound‐velocity measurements, and the other portion returned from the piston itself, giving the relative volume of the sample. In this way, adiabatic and isothermal compressibilities could be measured simultaneously. Relative volumes were also determined from the piston travel, observed externally. A calibrated manganin gauge allowed pressures to be compared with those calculated from the ram force and hysteresis curve of the advancing and retreating piston. Data are reported for argon at room temperature up to about 13 kbar where it solidifies.