See Also: Chemical Elements
(He), Gaseous Element, first observed spectroscopically in the Sun during a solar eclipse in 1868. Its noncombustibility and buoyancy make this
extremely unreactive, inert gas the most suitable of gases for balloons and
airships. Deep-sea divers often breathe a helium-and-Oxygen mixture; because helium is less soluble in human blood than Nitrogen, its use reduces the risk of the bends, or decompression sickness. Liquid
(see States Of Matter) helium is essential for low-Temperature work. Helium is also used in arc welding and gas-discharge Lasers. Abundant in outer space, helium is the product of Hydrogen fusion in Stars.