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Helium And Janssen

A French astronomer, Pierre-Jules-Csar Janssen (1824-1907), first obtained
evidence for the existence of helium during the solar eclipse of 1868 in India
when he detected a new yellow line (587.49 nm) in the solar spectrum very close
to the yellow sodium D-line. It was not possible to produce this line in the
laboratory. Sir Norman Lockyer (1836-1920), an English astronomer, recognised
that no known element at that time gave this line and named the element helium
for the sun. For many years helium was regarded as an element that might exist
on the sun although it was unknown on the Earth. Spectroscopists at the time
doubted the results concerning helium. However the claims initiated a search for
the new element on planet earth. In 1895, Sir William Ramsay discovered helium
after treating cleveite, a uranium mineral, with mineral acids. Ramsey sent
samples of the gas to Sir William Crookes and Sir Norman Lockyer who identified
helium. It was discovered independently in clevite by Cleve and Langley at about
the same time. Lockyer and Professor Edward Frankland suggested the name helium.

USES: ? filling balloons (blimps) as it is a much safer gas than hydrogen
? widely used as an inert gas shield for arc welding in countries where
helium is cheaper than argon ? protective gas in growing silicon and
germanium crystals, and in titanium and zirconium production ? cooling
medium for nuclear reactors ? a mixture of 80% helium and 20% oxygen is
used as an artificial atmosphere for divers and others working under pressure
? cryogenic applications as a gas for supersonic wind tunnels ? a
protective gas for semiconductor materials pressurizing liquid fuel rockets.

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