Occurrence of Helium
|Helium, like many other "rare" elements, is widely distributed in nature, though in most cases it is found only in small quantities. It is present in the atmosphere and in sea- and river-water, in the gases evolved from many mineral springs, and in most of the older rocks and minerals. It has been detected in at least one sample of meteoric iron; it exists, as already mentioned, in the sun; and spectroscopic observations lead to the conclusiqn that it is present in many other fixed stars and is indeed the chief constituent of the hottest of them. The lines of helium are also seen in the spectra of many nebulae and novae. |
The presence of helium in the atmosphere was detected spectroscopically first by Kayser at Bonn in August 1895 and, soon afterwards, by Friedlander at Berlin. Kamsay, using Dewar's method of separation (vide infra), found that air contained 0.000056 per cent, by weight and 0.00040 per cent, by volume of helium; i.e. about 1 volume of helium in 250,000 volumes of air; this, however, is obviously a minimum value, and Watson, from an analysis of the gas separated from air by Claude's method, concludes that the amount is more probably of the order of 1 volume in 185,000 volumes.
Helium has been detected in the gases evolved from many mineral springs. The following is a list of some of the more important: - . Five springs at Bois (Cauterets); several springs at Wildbad (Black Forest); Railliere (Pyrenees); Bagnoles de l'Orne; Monte Irone (Abano) and Casotto and Tini soffioni (Larderello, Tuscany); Mazieres, Cote d'Or, and many other springs; the Bath springs.
The gases at Mazieres contain 5.4 per cent, of helium, and might well serve as a source of the gas.
Cady and MacFarland have made a minute examination of a large number of samples (47) of natural gas from different localities in Kansas, U.S.A., especially with reference to the amounts of helium contained in them. Some helium was found in all but two samples, and the proportion present, in general, increased with increasing amounts of nitrogen and decreased with increase in the amount of paraffins. It is possible to trace lines of approximately equal content of helium and paraffins, and it is found that these run across the State from N.E. to S.W., and show a general correspondence with the lines of outcrop of the various geological strata. In four of the samples the amount of helium was over 1 per cent, by volume: -
|Dexter, Cowley Country||1.84 %|
|Dexter, Greenwell Well||1.64 %|
|Eureka, New Field||1.50 %|
|Eureka, Town Supply||1.50%|
It has been found that about 0.17 per cent, by volume of helium is contained in the inflammable gas which has for many years blown from a hole in the carnallite bed in the underground workings at Leopaldshall (Stassfurt). Similarly, both helium and argon have been found in gas blown off from the rock-salt at Karlsbad. Helium varying in amount from 0.0141 per cent, to 0.0014 per cent, occurs in the natural gases of Kissarm&s (Hungary), Pechelbronn, Wels (Austria), and Neuengamme (Hamburg): the gas from a deep well boring in Alsace contained 0.38 per cent, of helium. It has been calculated by Dr Johnstone Stoney that a gas having the low density of helium could not be retained permanently by a planet of the earth's mass; it seems probable that the constancy of the proportion of helium in the atmosphere is due to a balance between two factors - the loss of helium into space and its continual emission from sources such as those mentioned. It has been calculated that nine of the mineral springs investigated give off in the aggregate about 12,000 litres of the gas annually.
Helium is present, usually alone, but in some cases accompanied by argon, in a large number of minerals and rocks, and a considerable body of evidence has been accumulated which indicates that its presence is to be ascribed to the disintegration of radioactive material that is or has been contained in these substances. There is reason to believe that the helium in natural gas is mainly " fossil," and not of recent formation.
The most important helium minerals are: cleveite and other species of pitch-blende, monazite, fergusonite, broggerite, samarskite, thorianite, and euxenite. Other minerals in which helium has been found are: Naegite, yttrotantalite, annerodite, thalenite, malacone, carnotite, beryl, tobernite, wohlerite, pyrochlore, polycrase, trogerite, xenotime, gummite, thorite- orangeite, niobite-columbite, spliene, rutile, and zircon; also in the Stassfurt minerals, sylvine, carnallite, kieserite, and rock-salt, in native bismuth (Saxony), and in beryllium minerals.
The existence of helium in a meteorite (from Augusta County, Virginia, U.S.A.) affords additional evidence in favour of the conclusion that the element is widely distributed throughout our solar system.