Liquid Helium Vapor Pressure Equation

Abstract

An empirical equation for the vapor pressure of liquid helium has been developed. This equation is valid throughout the entire range of temperatures below the critical point, and is in accord with the latest available data on the vapor pressure to within about ±0.002°K.

Effect of theλTransition on the Atomic Distribution in Liquid Helium by Neutron Diffraction

“…A carbon resistor, 11 cemented into the base of the cassette, was used as a temperature sensitive element and calibrated against the liquid helium vapor pressure for temperatures down to 1.5°K using the T b5E scale. 12 Below 1.5°K the calibration was extrapolated using the semiconductor formula. 11 The temperature of the liquid helium was controlled and recorded by means of its vapor pressure as has been described.…”

Cryogenics

“…Clement et al (51) have examined in some detail the calibration of car bon resistors. It was, in fact, necessary to assume the correctness of three points on the vapour-pressure curve in order to derive a new scale and these were taken to be the normal boiling point on the 1948 scale and the temperatures of 1.6 and 2.9°K., determined by magnetic susceptibility measurements.…”

“…Clement has developed such a scale from the various U. S. experiments (38,39,40,43,44,49,51 ) and has prescribed the two possible measuring conditions for determining the vapour pressure: These deviations are of the order of a few millidegrees and appear to be connected with the experimental determination of vapour pressure, rather than with uncertainties in the absolute temperature.…”

An examination of the helium vapor-pressure scale of temperature using a magnetic thermometer

“…Possible errors in the 1948 scale were admi tted at t be time of its preparation, notably in the 1.3 0 to 2.2 0 K region from consideration of the helium isotherm measurements of Kistemaker [5], and b etween the normal boiling point and the critical point due to the sparsen ess of the experimental data upon which t he scale was based in the latter r egion. The investigations of Erickson and Roberts [6] with a magnetic thermometer for the region 1 0 to 4.20 K and those of Berman and Swenson [7] above 4.20 K with a gas thermometer provided a strong basis for a revision of the 1948 scale, and an empirical formula was developed by Clement and co"vorker s [8] from which a p-T table could be conveniently calculated to any desired precision, and which fitted the n ew data to within 0.002 deg throughout the en tire range. A summary of the situation obtaining in October 1954, prior to tbe development of the Clement formula and the publication of the supporting evidence obtained by Corak et a1.…”