Rubidium vapor pressure, high temperature

It is one of four metals — mercury, cesium, and rubidium — which can be liquid near room temperature and, thus, can be used in high-temperature thermometers. It has one of the longest liquid ranges of any metal and has a low vapor pressure even at high temperatures. 

Achener, P. Y., 1964, The Determination of the Latent Heat of Vaporization, Vapor Pressure, Enthalpy, and Density of Liquid Rubidium and Cesium up to 1,800°F, Proc. 1963 High Temperature Liquid Metal Heat Transfer Technology Meeting, Vol. 1, pp. 3-25 USAEC Rep. ORNL-3605. (2) Achener, P. Y, 1965, The Determination of the Latent Heat of Vaporization, Vapor Pressure of Potassium from 1,000-1,900°F, Aerojet-General Nucleonics Rep. AGN-8141. (2)... 

Bonilla, C. F., D. L. Sawhuey, and N. M. Makansi, 1962, Vapor Pressure of Alkali Metals III, Rubidium, Cesium, and Sodium-Potassium alloy up to 100 psia, Proc. 1962 High Temperature Liquid MetaI Heat Transfer Tech. Meeting, BNL-756, Brookhaven, NY. (3)... 

Because of the relatively high vapor pressure of the alkali metals compared with most other metals, distillation is an acceptable method of purification. Distillation under reduced pressure lowers the distillation temperature and thereby reduces the risk of contamination from the condenser. Vapor pressures increase from lithium to cesium (Table I). In the case of cesium (and also rubidium), the vapor pressure is sufficiently high that the type of glass still used for molecular liquids (e.g., water or alcohol) can be used for the alkali metal also. Removal of transition metals by distillation is virtually complete. With cesium, the high solubility of oxygen renders the filtration method unsuitable, whereas distillation is efficient. 

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