An Acoustical Thermometer for the Temperature Range 300–700 K

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Abstract
A fixed path ultrasonic interferometer, immersed in nitrogen gas at atmospheric pressure and utilizing a quartz crystal oscillating at 600 kHz, serves as a thermometer to define discrete temperatures in the range 300–700 K. The discrete points, occurring at intervals of 15–40°, are defined within ±0.12 and ±0.28 K, respectively, at the lower and upper limits of this range. In order to obtain this performance, it was necessary to measure certain gas phase properties, not available in the literature to sufficiently high precision, and also to utilize a sequence of data points in a least squares sense, thus obtaining lower standard deviations than those resulting from single observations.