THE RARE GASES

Evening Star, Issue 20982, 22 December 1931, Page 12

THE RARE GASES

A ROMANCE OF SCIENCE During tho early ’nineties of last century a well-known English scientist was carrying out experiments in his laboratory to find the exact densities of a number of different gases. One of tho gases with which he worked was nitrogen, and he was surprised to find that when it was prepared from air its density was always slightly higher than when it was prepared from chemicals. He could not understand the discrepancy, nor could he see any reason why the nitrogen from the two sources should be different. He therefore decided to seek the assistance of other scientists, and accordingly wrote to ‘ Nature,’ asking for suggestions. Tho letter was read by a' young professor of chemistry in London, and the interest it aroused in him led to a series of brilliant researches, by which tho explanation of the mystery was found. Lord Rayleigh was the scientist who wrote the letter, and Sir William Ramsay was tho chemist who, accepting the invitation and solving the problem, gave the sicentific world an unexpected thrill. Ramsay had at once suspected that Rayleigh’s atmospheric nitrogen was mixed with a small amount of some other gas, and he set out to find a means of separating the two. He had previously carried out experimental work with nitrogen, and the knowledge he had gained, enabled him to remove this gas from the supposed mixture. The result was promising. Ramsay obtained a small quantity of a gas which was denser than the original sample, and before long he was able, in collaboration with Rayleigh, to _ announce to a meeting of the British Association that a new gaseous element had been- found. The name argon, taken from the Greek argos, idle, was given to the gas, because it refused to combine with other elements, and exhibited a chemical inertness, which was at that time unique. In itself it was colourless, odourless, and tasteless. After Rayleigh had drawn attention to tho peculiarity of atmospheric nitrogen, there was found in the recorded experiments of tho Hon. Henry Cavendish, an eighteenth century chemist, whoso career was described in ‘Hie Age ’ of November 28, a statement that he had discovered that a small proportion of “phLgisticated air,” as atmospheric nitrogen was then called, differed- in its properties from the mam bulk. He had been unable to make it combine with oxygen by tho use of an electric spark, and he expressed the opinion that if any part of tho “ phlogisticated air’" was different from the rest it would not be more than l-120th of the whole. Ramsay found that ordinary air contains about 1 per cent, of argon, and his work substantiated the finding of this early scientist. Spurred on by this success Ramsay pursued his researches with unabating energy, and was rewarded by the discovery of four new elements, all of which were present in vei’y small amount in ordinary air. The first or these, helium, was discovered by Ramsay when examining traces of gas that were known to be present in ceitam rare minerals, hut he subs'?' quently discovered it in air. This gas, colourless and odourless like argon, had a romantic history. Years earlier its presence iu the sun s atmosphere was postulated from, an examination of tho solar spectrum and by a similar examination of the gases flaming from Mount Vesuvius its existence on earth was deducted; nothing was known of its’properties until it was isolated by Ramsay. Its name, derived from the Greek helios, sun, was given in virtue of its existence in tho sun’s atmosphere. Tho three other new gases, colourless, odourless, and equally as inert as argon and helium, were found by fractionally distilling large quantities of liquid air, and in an endeavour to make sure that no others should escape his notice Ramsay examined nearly 120 tons of this material. These latter gases were called neon, krypton, and xenon, the names being derived from the Greek words meaning “ new,” “ hidden,” and “ a stranger ” respectively. Ramsay’s triumph was complete; the discovery of this family of new elements was a scientific achievement of the first order, and academic honours were showered on him; he was knighted in 1902, received the Nobel prize for chemistry in 1904, and in 1911 was elected to the presidential chair of the British Association. But for years the rare gases of the atmosphere ■ remained laboratory ’ curios, stimulating tho interest of students of chemistry, but unknown by the world in general until the demands of war revived interest in one of them. During the years between its discovery by Ramsay and the outbreak of the World War helium had been found to exist in small quantities in tho gas that issued from some of the natural gas wells of North America, and when a light non-inflammable gas was required to fill observation balloons for service in Franco efforts were made to prepare helium in sufficient quantity from this source. Before the war the few cubic feet of the gai that were in existence were estimated to be worth about £4OO each, but by carrying out intensive researches the Americans succeeded in extracting helium from natural gas in sufficient quantity and at a price that made its use in balloons possible. The use of hydrogen as a lifting medium in balloons and airships is still common practice in countries other than tho United States, but is always accompanied by the risk of fire. The disaster to the British airship RlOl in Franco last year was made more terrible because of tho ignition of the hydrogen in her gasbags; and, in contrast, the superiority of helium for this purpose was demonstrated in a recent accident to tho American dirigible Shenandoah, which broke from her moorings in a gale and was severely damaged, but was eventually able to return to her hangar because the damage she suffered was not made worse by fire. Argon, too, has found an important use in industry, but its field of application is very different from that of helium. When electric light bulbs were first introduced into common use they consisted of a carbon filament in a glass bulb from which all air had been removed; these bulbs became blackened in use, and have been replaced by ones in which tho filament is of metal and the bulb contains a small amount of argon, or argon mixed with nitrogen. By this means the temperature of the filament can be raised and the efficiency of the light considerably improved.

Neon is the third of the inert series of gases to find its way into the service of the public, and it is used in the coloured glow tubes which form such a common feature of present-day advertising. The passage of electric currents through gases has been studied by chemists and physicists for many years, and they have found that different coloured glow effects are produced, depending on the gases used. Neon, when filled into glass tubes at low pressure and subjected to a potential difference of about 8,000 volts, gives a bright orange glow, and when the glass tubes arc bent into the shape of letters or diagrams they form a striking means of advertising* [lh@ ppm-!

bination of glow tubes producing different colours enables even more striking effects to bo produced, and helium, argon, and mercury vapour, in combination or alone, are the gases most commonly used with neon for this purpose. Orange light has the power of penetrating fogs, and for this reason neon lights are used as directional beacons on aerodromes in foggy weather; it is said that the red glow from these lights will penetrate a bank of cloud I,oooft in thickness. The thoroughness of Rayleigh and the brilliance of llamsay have given to the world a group of gases which affords a striking example of the potential value of an apparently abstruse academic research and a justification for the assertion of scientists that no knowledge is valueless, even though there is no scope for its immediate exploitation. There was no field for the commercial utilisation of helium, neon, and argon when they were discovered; that came only with the development of industry along lines that were not then apparent, and so it is that much scientific information which is at present without practical value may well be of great use in the future.—H.A.W., in the ‘ Age.’