A Constant Path Acoustic Interferometer for Gases at Variable Pressure

Abstract

A constant path acoustic interferometer is described, which operates by varying the pressure of the gas being studied. This variation in pressure results in the appearance of standing waves between the crystal and reflector. The resulting reaction peaks, detected by the usual methods, allow of determination of the wave‐length, and consequently the velocity, if the frequency be known. Comparison is made of the results on ethylene gas at 23.0°C and pressures between 35 to 55 atmospheres obtained with this instrument and those of a moving reflector interferometer. The two sets of data agree within the limits of error of the measurements.