Helium

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 …

…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