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(Gr. helios, the sun). Janssen obtained the first evidence of helium during the solar
eclipse of 1868 when he detected a new line in the solar spectrum. Lockyer and Frankland
suggested the name helium for the new element. In 1895 Ramsay discovered helium in the
uranium mineral clevite while it was independently discovered in cleveite by the Swedish
chemists Cleve and Langlet at about the same time. Rutherford and Royds in 1907
demonstrated that alpha particles are helium nuclei.
Except for hydrogen, helium is the most
abundant element found through out the universe. Helium is extracted from natural gas. In
fact, all natural gas contains at least trace quantities of helium.
It has been detected spectroscopically in great abundance, especially in the hotter
stars, and it is an important component in both the proton-proton reaction and the carbon
cycle, which account for the energy of the sun and stars.
The fusion of hydrogen into helium provides the energy of the hydrogen bomb. The helium
content of the atmosphere is about 1 part in 200,000. While it is present in various
radioactive minerals as a decay product, the bulk of the Free World's supply is obtained
from 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
The cost of helium fell from $2500/ft3
in 1915 to 1.5 cents /ft3
in 1940. The U.S. Bureau of Mines has set the price of Grade A helium at $37.50/1000 ft3 in 1986.
Helium has the lowest melting point of any element and is widely used in cryogenic
research because its boiling point is close to absolute zero. Also, the element is vital
in the study of super conductivity.
Using liquid helium, Kurti and co-workers and others, have succeeded in obtaining
temperatures of a few microkelvins by the adiabatic demagnetization of copper nuclei.
It has other peculiar properties. Helium is the only liquid that cannot be solidified
by lowering the temperature. It remains liquid down to absolute zero at ordinary
pressures, but it can readily be solidified by increasing the pressure. Solid 3He and 4He
are unusual in that both can be changed in volume by more than 30% by applying pressure.
The specific heat of helium gas is unusually high. The density of helium vapor at the
normal boiling point is also very high, with the vapor expanding greatly when heated to
room temperature. Containers filled with helium gas at 5 to 10 K should be treated as
though they contained liquid helium due to the large increase in pressure resulting from
warming the gas to room temperature.
While helium normally has a 0 valence, it seems to have a weak tendency to combine with
certain other elements. Means of preparing helium difluoride have been studied, and
species such as HeNe and the molecular ions He+ and He++ have been investigated.
Seven isotopes of helium are known: Liquid helium (He4) exists in two forms: He4I and
He4II, with a sharp transition point at 2.174K. He4I (above this temperature) is a normal
liquid, but He4II (below it) is unlike any other known substance. It expands on cooling;
its conductivity for heat is enormous; and neither its heat conduction nor viscosity obeys
- as an inert gas shield for arc welding;
- a protective gas in growing silicon and germanium crystals and producing titanium and
- 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. Different ratios of He/O2 are used for different depths at
which the diver is operating.
Helium is extensively used for filling balloons as it is a much safer gas than
hydrogen. One of the recent largest uses for helium has been for pressuring liquid fuel
rockets. A Saturn booster, like the type used on the Apollo lunar missions, required about
13 million ft3 of helium
for a firing, plus more for checkouts.
Liquid helium's use in magnetic resonance imaging (MRI) continues to increase as the
medical profession accepts and develops new uses for the equipment. This equipment has
eliminated some need for exploratory surgery by accurately diagnosing patients. Another
medical application uses MRE to determine (by blood analysis) whether a patient has any
form of cancer.
Helium is also being used to advertise on blimps for various companies, including
Goodyear. Other lifting gas applications are being developed by the Navy and Air Force to
detect low-flying cruise missiles. Additionally, the Drug Enforcement Agency is using
radar-equipped blimps to detect drug smugglers along the United States boarders. In
addition, NASA is currently using helium-filled balloons to sample the atmosphere in
Antarctica to determine what is depleting the ozone layer.
Materials which become super conductive at higher temperatures than the boiling point
of helium could have a major impact on the demand for helium. These less costly
refrigerant materials could replace the present need to cool superconductive materials to
the boiling point of helium.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.