Helium - 2He: historical information
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.