Compression and Phase Transitions of Solid NH3, SiF4, H2S, and CF4

Abstract

Isothermal PV curves of solid NH3, SiF4, H2S, and CF4 have been observed by the direct piston displacement method up to pressures of 20 000 kg/cm2 at various temperatures between 100° and 200°K. Relative volume changes and compressibilities are given for each substance except CF4. Phase transitions have been observed as discontinuities in the piston motion. NH3 exhibits no phase transitions. Phase diagrams are given for the other three substances. Comparison with previous work in the case of H2S shows only partial agreement. In some instances the approximate volume changes accompanying the phase transitions have been determined.