-268.93°C = -452.074°F = 4.22 K
-267.96°C = -450.328°F = 5.19 K
= °F = K
0.49Å (Å = Angstrom = 10-10 m)
(Gr. helios, the sun). Janssen obtained the first evidence
of helium during the solareclipse of 1868 when he detected
a new line in the solar spectrum. Lockyer and Franklandsuggested
the name helium for the new element. In 1895 Ramsay discovered
helium in theuranium mineral clevite while it was independently
discovered in cleveite by the Swedishchemists Cleve and
Langlet at about the same time. Rutherford and Royds in
1907demonstrated that alpha particles are helium nuclei.
Except for hydrogen, helium is the mostabundant element
found through out the universe. Helium is extracted from
natural gas. Infact, all natural gas contains at least trace
quantities of helium.
It has been detected spectroscopically in great abundance,
especially in the hotterstars, and it is an important component
in both the proton-proton reaction and the carboncycle,
which account for the energy of the sun and stars.
The fusion of hydrogen into helium provides the energy
of the hydrogen bomb. The heliumcontent of the atmosphere
is about 1 part in 200,000. While it is present in variousradioactive
minerals as a decay product, the bulk of the Free World's
supply is obtainedfrom wells in Texas, Oklahoma, and Kansas.
The only known helium extraction plants,outside the United
States, in 1984 were in Eastern Europe (Poland), the USSR,
and a few in India.
Helium is widely used in cryogenic research because its
boiling point is near absolute zero. It is used in the study
of superconductivity, as an inert gas shield for arc welding,
as a protective gas in growing silicon and germanium crystals
and producing titanium and zirconium, for pressuring liquid
fuel rockets, for use in magnetic resonance imaging (MRI),
as a cooling medium for nuclear reactors, and as a gas for
supersonic wind tunnels. A mixture of helium and oxygen
is used as an artificial atmosphere for divers and others
working under pressure. Helium is used for filling balloons