THE increasing importance of neon as a cryogenic liquid has led to a greater interest in its properties at low temperatures. Certain advantages of neon over hydrogen and helium as a liquid refrigerant have been pointed out,1 and it has been used in infra-red detectors, minicoolers, and cryogenic magnets. The possibility of using mixtures of neon and hydrogen to obtain shorter radiation lengths in hydrogen bubble chambers has also been considered.* Air contains about 18 p.p.m. of neon and is almost the sole source of supply. Since neon can be produced by air separation plants, phase equilibrium data on several neon systems should be useful in promoting the efficiency of the recovery process.
A survey of the literature on low temperature phase equilibria reveals few studies of systems in which neon is a component. The comprehensive bibliography of Flynn,3 published in 1960, includes no references to systems containing neon. Karasz and Halsey4 studied the solubility of neon in liquid argon; however, their data are limited to neon partial pressures of 15 cm of mercury or less. Recently, Brownings obtained a limited amount of data on the neonargon system, using a dew-and bubble-point apparatus. Browning's data include only a few points in the liquid region, all for mixtures of 0.23 per cent neon in argon. Simon6 has published a single isotherm, 24.56" K, for the system neon-parahydrogen.
For the neon-nitrogen system, Burch' has published data for two isotherms, 82.70 and 113.13" K, at pressures from 6.4 to 50 atm; a comparison of his data with the present work is given below.
In this work, compositions of liquid-vapour phase equilibrium for the system neon-nitrogen have been determined at nine temperatures, covering the range 66.13-120.64" K, and at pressures up to 1,000 lb/in* absolute. Equipment A schematic diagram of the experimental equipment is shown in Figure 1. It is similar to equipment used by this author in a recent study of the hydrogenhelium system,819 and is based on an original design by Dodge and Dunbar.lO CRYOGENICS.