Commonly known as a fill gas for colourful neon signs, neon gas fulfils a whole range of other uses and applications.
“I smelled Los Angeles before I got to it. It smelled stale and old like a living room that had been closed too long. But the coloured lights fooled you. The lights were wonderful. There ought to be a monument to the man who invented neon lights. Fifteen stories high, solid marble. There is a boy who really made something out of nothing.” Raymond Chandler, The Little Sister
Neon, which mean ‘New one’ in Greek, was discovered in 1898 by Scottish chemist Sir William Ramsay and English chemist Morris in London, UK.
Neon was discovered when Ramsay chilled a sample of the atmosphere until it became a liquid, then warmed the liquid and captured the gases as they boiled-off. The three gases that boiled off were krypton, xenon and neon.
In 1910, Frenchman Georges Claude made a lamp from an electrified tube of neon gas and soon began selling his tubes to US companies in 1915.
Although a very common element in the universe and perhaps the most aesthetically ‘colourful’ of all the gases, it is actually rare on Earth and in fact, a colourless, inert noble gas under standard conditions.
Neon gives a distinct reddish-orange glow when used in discharge tubes and neon lamps and is the second-lightest noble gas. Commercially extracted from air, where it is found in trace amounts, neon is also the least reactive noble gas and thus, the least reactive of all elements.
On a per unit volume basis, neon has over 40 times the refrigerating capacity of liquid helium and three times that of liquid hydrogen – enabling use in many applications as a less expensive refrigerant than helium.
Occurrence & production process
Neon is actually abundant on a universal scale: the fifth most abundant chemical element in the universe by mass, after hydrogen, helium, oxygen, and carbon.
Its relative rarity on Earth, like that of helium, is due to its relative lightness and chemical inertness, both properties keeping it from being trapped in the condensing gas and dust clouds of the formation of smaller and warmer solid planets like Earth.
The liquefaction of air is a large-scale process, providing the primary source of liquid nitrogen and oxygen. These two gases liquefy at temperatures that are well above the boiling point of neon.
However, this means neon, as well as a few other gases, remains as gaseous residues in air-liquefaction processes. Commercially, neon is produced as a secondary product at liquid nitrogen/oxygen plants.
Commonly known as a fill gas for colourful neon signs in outdoor advertising displays, neon’s other uses include glow lamps as visual indicator devices, voltage regulation, and lasers.
In combination with other rare gases, neon has found increased application in special fluorescent lamps and is also used in spark chamber mixtures, useful in atomic particle research.
Liquid neon has properties unique amongst other low-temperature cryogenic fluids, in that its latent heat of vaporisation is almost double that of helium and 20 times that of hydrogen. It also has the greatest gas-to-liquid ratio of the atmospheric gases, 1445:1, ensuring that one liquid litre at room temperature will evolve 1,445 gas litres.
With more than 30 times the refrigerant capacity, per unit of volume, of liquid helium, liquid neon is an economical cryogenic refrigerant. It is however, also quite expensive to obtain in small quantities due to the rarity of the gas and not the liquefaction process.
Neon is also used in the manufacture of electrical and electronic equipment, such as lightning arrestors, high-voltage indicators, television tubes and lasers. Currently, there is an increased interest in the use of neon as a coolant, arising from its physical properties including its low boiling temperature, which allows cooling to temperatures in the range 24°-43° K.
In addition, neon’s status as an inert gas also provides advantages – all of its properties are similar to those of liquid hydrogen, with the exception of non-combustibility.