NEON. In 1898, Sir William Ramsey dis covered this gas in the atmosphere. He secured it by means of the distillation of liquefied air. Claude has since developed the process of sep aration of the elements of the air by liquefac tion to a point which allows the production of Neon as an industrial product suitable for use for commercial purposes. Neon is found in the atmosphere in the very small proportion of one part of Neon to 66,000 parts of air. It belongs to the group of inert gases, i.e., those which do not combine chemically with other elements, and, like the other inert gases, is monatomic. Its valence is 0.
Physical Properties.— Chemical symbol, Ne.
Colorless, odorless, tasteless.
Atomic weight, 202.
Specific gravity, 0.695 (Air=1).
Boiling point, —243° C.
Melting point, —253° C.
Critical temperature, <-205° C.
Critical pressure, 29 atmospheres. Spectrum consists of green lines and several orange lines.
Neon has been proved to be monatomic by determining the ratio of its specific heat at con stant pressure to its specific heat at constant volume.
Commercial Uses.— When a tube contain ing Neon is rarefied it is readily permeated by an electric discharge. Neon has found a limited use commercially as a gas for filling tubes for the production of light by the passage of an electric current through the tube. Difficulties
have been met in employing it in this way be cause it is sensitive to the presence of the smallest quantities of other gases, and its lumin ous properties are entirely overcome by them. Claude has devised a process of removing this difficulty by utilizing the absorbent properties of charcoal when cooled, which were discovered by Dewar. This is done by purifying the Neon in the tube during the passage of the electric current, by means of charcoal, the temperature of which has been lowered by liquid air. When the impurities have been removed in this man ner and the Neon left, the tube is separated from the charcoal receptacle.
Neon tubes used in lighting have an advan tage over nitrogen tubes in that the candle power is much greater and the efficiency better. A disadvantage is that the light produced is too red because there is an absence of blue rays. This quality is desirable, however, in display illumination where the dazzling light produces a beautiful effect. Neon tubes were used in 1910 in Paris for lighting the Grand Palace on the Champs Elysies. Their use, however, has not been developed commercially to any extent.