helium Chem.
(ˈhiːlɪəm)
[mod.L., f. Gr. ἥλιος sun, with the termination already used in selenium, tellurium, etc.]
a. One of the chemical elements, a transparent gas, first actually obtained by Prof. Ramsay in 1895, its existence in the sun's atmosphere having been inferred by Lockyer in 1868 from a certain line (D3) in the spectrum of the solar prominences. (Cf. coronium.) Symbol He.
| 1872 W. Thomson in Rep. Brit. Assoc. p. xcix, Frankland and Lockyer find the yellow prominences to give a very decided bright line not far from D, but hitherto not identified with any terrestrial flame. It seems to indicate a new substance, which they propose to call Helium. 1878 Newcomb Pop. Astron. iii. ii. 266 This hydrogen is always mixed with another substance, provisionally called helium. 1884 Longm. Mag. Apr. 599 The orange-yellow tint of helium. 1895 Daily News 28 Mar. 7/7 As he had anticipated, argon was given off and not nitrogen, but mixed with it he found what appeared to be another gas. This gas is no other than the hypothetical Helium, whose existence has only been inferred up to the present from a line D 3 in the solar spectrum. 1897 Lockyer Sun's Place in Nat. iv, The Discovery of Helium. 1955 Sci. Amer. Oct. 61/1 Helium is an ideal cooling gas, because it has a high specific heat and does not capture neutrons, but it is very expensive and is not available in large quantities in Great Britain. 1958 Chambers's Techn. Dict. 984/2 Helium, proposed coolant for reactors because of negligible cross-section for neutrons. |
b. attrib. and Comb., as helium atom, helium content, etc.; helium star, a star which exhibits the helium lines in its spectrum.
| 1903 A. M. Clerke Probl. Astrophysics 93 A helium-envelope surrounds the sun to a depth of five thousand miles. Ibid. 94 Now that the helium-spectrum has been unravelled. 1904 Goodchild & Tweney Technol. & Sci. Dict. 284/2 Helium stars, stars the spectra of which show prominently the lines of the gas helium. 1920 Discovery Apr. 111/1 Helium determinations never can provide data for more than a minimum estimate [of the age of a mineral]. All that the helium-ratio can tell us is that the age of the mineral to which it refers is greater than a certain minimum value. 1921 Ibid. Sept. 236/1 The B or helium stars are on the crest of the evolutionary curve, at the meridian of stellar life. 1926 R. W. Lawson tr. Hevesy & Paneth's Man. Radioactivity xxvi. 216 (heading) Age determination from the helium content. 1938 Ibid. (ed. 2) xxv. 267/2 When the ‘helium method’ was first applied to minerals, it gave values for the age which were mostly only about one-half or one-third of the values found by the ‘lead method’. 1940 Chambers's Techn. Dict. 409/1 Helium diving bell, a diving bell in which the nitrogen in the compressed-air is replaced by helium, thus reducing tendency to the bends. 1956 A. H. Compton Atomic Quest iii. 163 The only plans for a production plant..were those of Moore's helium-cooled reactor. 1957 Gloss. Terms Nucl. Sci. (Nat. Res. Council U.S.) 7/1 s.v. Age, If the age is calculated from the relative number of atoms of a stable radiogenic end product and radioactive parent present, the method is designated by the name of the end product. Examples are the lead age and helium age of a uranium-containing and/or thorium-containing mineral. 1957 Technology Mar. 14/2 In the hydrogen bomb the energy generated is derived from the fusion of hydrogen atoms into helium atoms. 1958 F. E. Zeuner Dating Past (ed. 4) 329 Were there not certain difficulties connected with the gaseous nature of helium, age estimates could be carried out with the helium generated by radioactive substances just as well as with the lead. The amount of helium present is determined and compared with the amount of uranium (and thorium) contained in the mineral, in other words, the helium-ratio is determined. Ibid. 427 A sample of magnetite from Larder Lake District..has yielded a helium-age of 2,400 million years. 1960 Nature 24 Sept. 1077/1 At the meeting of the International Committee of Weights and Measures held in Sevres, during September 29–October 3, 1958, the recommendation was adopted that the ‘1958 Helium-4 Vapour Pressure Scale of Temperatures’..should be used as the international standard scale of temperature between 1° and 5·2°K. |