EQUATION OF STATE OF NEON BETWEEN 27-K AND 70-K

Accurate PVT data were measured at low temperatures and high pressure by means of a specially constructed apparatus. The results of preliminary experiments with nitrogen at 72·3 K and 77·9 K agreed with the values of Van Itterbeek and Verbeke, and established that the accuracy of the data was of the order of 0·15%. Other preliminary experiments showed that the capacity of the fill tube as a function of temperature and pressure could be calculated to within 2% for both nitrogen and neon. This apparatus was used to measure 309 points on the PVT surface of neon between 27 K and 70 K, at pressures of up to 200 atm. From these data the saturated liquid and vapour densities, the entropy, enthalphy, second and third virial coefficients of the gas were calculated at several temperatures. The McCarty-Stewart equation agreed well with the data in the gas phase but was considerably in error for the liquid phase. There were systematic discrepancies of up to 2% in the compressibility factor between these measurements and the data of Sullivan and Sonntag at 70 K, but the saturated densities obtained agreed well with the data of Mathias, Crommelin, and Onnes. © 1969.