A very heavy, inert gaseous element occurring in the atmosphere in the proportion of one volume is about 20 millions. It was discovered by Ramsay and Travers in 1898. It can be condensed to a liquid boiling at -109° C., and to a solid which volatilizes without melting. Symbol Xe or X; atomic weight 130.2.
- A colorless, odorless, highly unreactive gaseous element found in minute quantities in the atmosphere, extracted commercially from liquefied air and used in stroboscopic, bactericidal, and laser-pumping lamps. Atomic number 54; atomic weight 131.29; melting point -111.9°C; boiling point -107.1°C; density (gas) 5.887 grams per liter; specific gravity (liquid) 3.52 (-109°C). See Table at element.