Device for measuring sound speeds in reactive liquids at high pressure and temperature

We have designed a device for measuring sound speeds in reactive liquids at high pressure and temperature. It has been tested in experiments on liquid-potassium metal at pressures up to 0.7 GPa and temperatures up to 423 K. The limitations on pressure and temperature were imposed by auxiliary instrumentation rather than the properties of the device, and it seems likely that it would be suitable for more extreme conditions. The data on potassium agree well with precise room-temperature data. The sound velocities measured as a function of pressure at various temperatures can be used to calculate equation-of-state parameters such as the bulk modulus and its pressure derivatives. The experiments on potassium indicate that bulk modulus can be determined to ±1%, its first pressure derivative to about ±5%, and second pressure derivative to about ±50% (the last for a run with a 0.7-GPa pressure range). The device should permit sound velocity measurements in a variety of liquids which are reactive, corrosive, and/or miscible with pressure media.