is a colorless, odorless, tasteless chemical element. It is the most
unreactive of the noble gases and therefore the least chemically-active
chemical element on the periodic table. Its boiling and melting points
are the lowest among the elements; except in extreme conditions, it
exists only as a gas. At temperatures near absolute zero, it is a superfluid,
a nearly frictionless phase of matter with unusual properties.
hydrogen, helium is the
second lightest element and the second most abundant element in the
universe, created during big bang nucleosynthesis and to a lesser extent
from nuclear fusion of hydrogen in stars. On Earth, helium is primarily
a product of the radioactive decay of much heavier elements, which emit
helium nuclei called alpha particles; it is found in significant amounts
only in natural gas, from which it is extracted at low temperatures by
detected in 1868 by French astronomer Pierre Janssen as an unknown
yellow spectral line signature in the light of a solar eclipse, helium
was separately identified as a new element later that year by English
astronomer Norman Lockyer. Its presence in natural gas in large, useable
amounts was identified in 1905. Helium is used in cryogenics, as a
deep-sea breathing gas, for inflating balloons and airships, and as a
protective gas for many industrial purposes, such as arc
welding. Inhaling a small amount of the gas temporarily changes the
frequency of a person's voice; however, caution must be exercised as
helium is an asphyxiant.
of its low density, helium is the gas of choice
fill airships such as the Holden Airship
is used for many purposes that require some of its unique properties,
such as its low boiling point, low density, low solubility, high thermal
conductivity, or inertness. Pressurized helium is commercially available
in large quantities.
it is lighter than air, airships and balloons are inflated with
helium for lift. In airships, helium is preferred over hydrogen
because it is not flammable and has 92.64% of the lifting power of
the alternative hydrogen.
its low solubility in water, the major part of human blood, air
mixtures of helium with oxygen
and nitrogen (Trimix),
with oxygen only (Heliox), with common air (heliair),
and with hydrogen and
oxygen (hydreliox), are used in deep-sea breathing systems to
reduce the high-pressure risk of nitrogen narcosis, decompression
sickness, and oxygen toxicity.
extremely low temperatures, liquid helium is used to cool certain
metals to produce superconductivity, such as in superconducting
magnets used in magnetic resonance imaging. Helium at low
temperatures is also used in cryogenics.
its inertness and high thermal conductivity, helium is used as a
coolant in some nuclear reactors, such as pebble-bed reactors, and
in arc welding air-sensitive metals.
it is inert, helium is used as a protective gas in growing silicon
and germanium crystals, in titanium and zirconium production, in gas
chromatography, and as an atmosphere for protecting historical
documents. This property also makes it useful in supersonic wind
rocketry, helium is used as an ullage medium to displace fuel and
oxidizers in storage tanks and to condense hydrogen and oxygen
to make rocket fuel. It is also used to purge fuel and oxidizer from
ground support equipment prior to launch and to pre-cool liquid
hydrogen in space
vehicles. For example, the Saturn V booster used in the Apollo
program needed about 13 million cubic feet (370,000 m³) of helium
gain medium of the helium-non laser is a mixture of helium and neon.
it diffuses through solids at a rate three times that of air, helium
is used to detect leaks in high-vacuum equipment and high-pressure
of its extremely low index of refraction, the use of helium reduces
the distorting effects of temperature variations in the space
between lenses in some telescopes.
age of rocks and minerals that contain uranium and thorium,
radioactive elements that emit helium nuclei called alpha particles,
can be discovered by measuring the level of helium with a process
known as helium dating.
helium alone is less dense than atmospheric air, it will change the
timbre (not pitch ) of a person's voice when inhaled. However,
inhaling it from a typical commercial source, such as that used to
fill balloons, can be dangerous due to the number of contaminants
that may be present. These could include trace amount of other
gases, in addition to aerosolized lubricating oil.
high thermal conductivity and sound velocity of helium is also
desirable in thermoacoustic refrigeration. The inertness of helium
adds to the environmental advantage of this technology over
conventional refrigeration systems which may contribute to ozone
depleting and global warming effects.
Elements: Third Edition, by John Emsley (New York; Oxford
University Press; 1998; pages 94-95) ISBN 0-19-855818-X
States Geological Survey (usgs.gov): Mineral
Information for Helium (PDF)
thermosphere: a part of the heterosphere, by J. Vercheval
Composition and Abundance of Interstellar Neutral Helium Based on
Direct Measurements, Zastenker G.N. et al., ,
published in Astrophysics,
April 2002, vol. 45, no. 2, pp. 131-142(12)
and thermodynamic properties of solid helium in the reduced
all-neighbours approximation of the self-consistent phonon theory,
C. Malinowska-Adamska, P. Sŀoma, J. Tomaszewski, physica
status solidi (b), Volume 240, Issue 1 , Pages 55 - 67
Two Fluid Model of Superfluid Helium, S. Yuan,
Film Rates in Liquid Helium, Henry A. Fairbank and C. T. Lane,
Phys. Rev. 76, 1209–1211 (1949), from
the online archive
to Liquid Helium, at the NASA Goddard Space Flight Center
of vacuum VS helium in a solar telescope, Engvold, O.;
Dunn, R. B.; Smartt, R. N.; Livingston, W. C.. Applied Optics,
vol. 22, 1 January 1983, p. 10-12.
of Mines (1967). Minerals yearbook mineral fuels Year 1965,
Volume II (1967). U. S. Government Printing Office.
Fundamental models, Don L. Anderson, G. R. Foulger &
Pressure Nervous Syndrome, Diving Medicine Online
and Isotopes Fourteenth Edition: Chart of the Nuclides,
General Electric Company, 1989
Encyclopedia of the Chemical Elements, edited by Cifford A.
Hampel, "Helium" entry by L. W. Brandt (New York; Reinhold
Book Corporation; 1968; page 261) Library of Congress Catalog Card
Alamos National Laboratory (LANL.gov): Periodic Table, "Helium"
John. Nature's Building Blocks: An A-Z Guide to the Elements.
Oxford: Oxford University Press, 2001. Page 178. ISBN 0-19-850340-7
Encyclopedia of the Chemical Elements, page 262
Encyclopedia of the Chemical Elements, page 263
Physics in speech
Encyclopedia of the Chemical Elements, page 256
Encyclopedia of the Chemical Elements, page 257
Nature's Building Blocks, 177
Nature's Building Blocks, 179
Chemical Society (2004). The
Discovery of Helium in Natural Gas.
to the Elements: Revised Edition, by Albert Stwertka (New York;
Oxford University Press; 1998; page 24) ISBN 0-19-512708-0
Periodic Table: Professional Edition: Helium: key information
Encyclopedia of the Chemical Elements, page 258
States Geological Survey (January 2006). Mineral
Commodity Summaries: Helium.
Encyclopedia of the Chemical Elements, page 264
Encyclopedia of the Chemical Elements, page 260
taste for adventure capitalists
Cola - a healthier alternative