An element discovered by the English
chemists
Sir William Ramsay and
Morris Travers in
1898, using
fractional distillation. It is one of the
noble gasses. Its symbol is
Kr, and its atomic number is 36.
He took the name from the Greek word kryptos, meaning hidden.
Its main use in is neon lights, in which it is used to make a pale violet. It is also often used for airport runway lights. Since it also has a fast response time to electric currents, it is often used with xenon in high-intensity, sort-exposure photographic flash bulbs and in strobe lights.
In 1960 an international committee decided to use the wavelength of one of the colors of krypton-86 to define the meter. A meter was exactly 1,650,762.73 wavelengths of the red-orange spectral line of krypton-86. The meter has since been redefined as 1/299,792,458 of the distance light (in a vacuum) travels in a second.