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DISCOVERY:
A French astronomer, Pierre-Jules-César 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
Bibliography
none
Word Count: 278
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