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Helium is a commonly used carrier gas for gas chromatography. The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating. [28] [30] Helium at low temperatures is used in cryogenics and in certain cryogenic applications.
Terrestrial helium consists almost exclusively (all but ~2ppm) [16] of 4 He. 4 He's boiling point of 4.2 K is the lowest of all known substances except 3 He. When cooled further to 2.17 K, it becomes a unique superfluid with zero viscosity. It solidifies only at pressures above 25 atmospheres, where it melts at 0.95 K.
Terrestrial helium was found about 27 years later by the Scottish chemist William Ramsay. In his work on the identification of helium, Lockyer collaborated with the noted chemist Edward Frankland. [14] To facilitate the transmission of ideas between scientific disciplines, Lockyer established the general science journal Nature in 1869. [15]
The helium abundance is 0.157 ± 0.004 relative to molecular hydrogen by number of molecules, and its mass fraction is 0.234 ± 0.005, which is slightly lower than the Solar System's primordial value. [1] The reason for this low abundance is not entirely understood, but some of the helium may have condensed into the core of Jupiter. [21]
[18] [19] Samples of the lithium ore spodumene from Edison Mine, South Dakota were found to contain 12 parts of helium-3 to a million parts of helium-4. Samples from other mines showed 2 parts per million. [18] Helium is also present as up to 7% of some natural gas sources, [20] and large sources have over 0.5% (above 0.2% makes it viable to ...
Parts of icy Antarctica are turning green with plant life as the region is gripped by extreme heat events, new research shows, sparking concerns about the changing landscape on this vast continent.
Pages in category "Isotopes of helium" The following 10 pages are in this category, out of 10 total. This list may not reflect recent changes. ...
Liquid helium is a physical state of helium at very low temperatures at standard atmospheric pressures.Liquid helium may show superfluidity.. At standard pressure, the chemical element helium exists in a liquid form only at the extremely low temperature of −269 °C (−452.20 °F; 4.15 K).