Krypton

Krypton is a colorless, odorless noble gas that makes up only about one part per million of the air. William Ramsay and Morris Travers discovered it in 1898 by slowly boiling liquid air, naming it from the Greek for hidden. It is still collected from air the same basic way, as a byproduct of making oxygen and nitrogen.

Krypton fills the gap in some high-performance windows, where its heaviness slows heat loss. It is used in some lamps, photographic flashes and lasers, including the krypton fluoride lasers used to pattern chips. From 1960 to 1983, the meter was officially defined by the wavelength of an orange line in krypton's light.