Vapor Pressures of Natural Neon and of the Isotopes20Ne and22Ne from the Triple Point to the Normal Boiling Point

Abstract

Apparatus design and procedures are described for the determination of the vapor pressures of naturally occurring neon (^natNe) and the pure isotopes ²⁰Ne and ²²Ne from their triple points (TP) to their normal boiling points (NBP). The data have been fitted to vapor-pressure equations with root-mean-square deviations of ± 2.5 to ± 4.7 N/m² (± 0.019 to ± 0.035 mmHg). The TP pressures (P) and the TP and NBP temperatures (T) were found to be: TP NBP P T, K T, K ^natNe 43332 ± 13 N/m² (325.02 ± 0.10 mmHg) 24.553 ± 0.001 27.096 ±0.001 ²⁰Ne 43326 ± 13 N/m² (324.97 ± 0.10 mmHg) 24.540 ± 0.001 27.084 ± 0.001 ²²Ne 43654 ± 13 N/m² (327.43 ± 0.10 mmHg 24.687 ± 0.001 27.211 ± 0.001 (The temperatures are in terms of the NBS-1955 provisional temperature scale. The figures after the ± symbol indicate estimated uncertainties). The calculated vapor pressures of the isotopic ^natNe, based on Raoult's law of solution and the observed vapor pressures of the pure isotopes, are in agreement within the combined precision of the measurements with the observed values of ^natNe.