Noble Gas Xenon, Xe

By efforts of many of scientists, especially of Morris Travers, significant amounts of liquid air became accessible. Liquid xenon also became available for scientists, due to which William Ramsay and Morris Travers obtained an opportunity to start research of the residue left over from evaporating of such components of liquid air as helium, hydrogen, neon, oxygen, nitrogen and argon. It contained raw krypton. However, after evaporating krypton there was still a bubble with some gas in the vessel. The gas was emitting a blue glow when excited by electrical discharge and produced extremely very unusual, full-spectrum, from orange to violet, white light. These spectrum lines are the carte-de-visite of this element. Ramsay and Travers had all good reasons to suppose that a new element, inert, or noble gas, had been discovered. It was called xenon, from a Greek word meaning "strange one" or "stranger"; it was a stranger indeed in krypton fraction.

Abundance in atmosphere is 0.86x10^-5 % by volume; deposits are estimated as 1.6-10¹¹ m³. It is of limited occurrence in space: 1 xenon atom per 7.7x10⁸ helium atoms. It is contained in gaseous inclusions of uranium-bearing minerals, up to 20% by mass, as well as in irradiated fuel of nuclear reactors.

Xenon is produced as a by-product of air fractions separation. It may be extracted from krypton-xenon concentrate. Manufactured xenon is graded as pure, 99.4% by volume, and high-pure, 99.9%.

Hitherto xenon has usually been obtained along with krypton in the heavy residues from the evaporation of large quantities of liquid air. The mixture is fractionated according to methods described under Krypton, and the heaviest and most easily condensed fractions are fairly pure xenon.

Xenon may also be obtained from pure dry air, free from carbon dioxide and moisture, by the simple plan of passing it, under suitable reduced pressure, through a spiral tube filled with glass-wool immersed in a bath of liquid air. If the conditions are carefully regulated it is possible to obtain the greater part of the xenon present in the air condensed as a solid in the glass-wool.

Xenon is more easily purified than krypton as it is always accumulated in the end fractions. Moreover, the vapour pressure of the solid at the temperature of liquid air is so small (0T7 mm.) that all other gases may be pumped off from it. It is usually found that while the greater part of the more volatile gases may be removed in one operation, a small portion is occluded by the solid xenon. If, however, the solid be allowed to warm up and then again cooled, the occluded gas is liberated and can be pumped off.