Helium uraninite

The element helium, from Greek helios, the sun, had already been noted in the Sun s spectrum in 1868, but was not isolated as a terrestrial element until 1895, when Ramsay obtained it by heating the mineral uraninite in which the helium was physically trapped. With an improved technique of liquid air distillation, Ramsay and Travers isolated neon (Greek, neos, new), krypton (Greek, kryptos, hidden), and xenon (Greek,... 

Helium was recognised as an element in 1895, but the history of its discovery dates back a further 30 years. The bright yellow He lines in the solar spectrum were first noted, but not identified, in 1868. In 1888, helium liberated when uraninite is treated with acid was mistaken for another inert gas, nitrogen. 

History. Helium was discovered by spectroscopic studies conducted by Jansen on the solar protuberance observed during the solar eclipse of 1868 and it was named by Frankland and Lockwood from the Greek, helios, for Sun. Later, helium was identified by Kayser in the Earth s atmosphere and by Sir William Ramsay by dissolving the uranium mineral cleveite today known as uraninite [UO, tetragonal or metamict] into acids. 

Discovery The French astronomer P. J. C. Janssen found a yellow line in the solar spectrum in 1868. As it did not belong to sodium, hydrogen or any other known element, a new element had been discovered. It was named helium due to its origin in the sun. In 1895 Ramsay in England as well as Cleve and Langlet in Sweden discovered helium in the mineral cleveite, a uraninite with high content of rare earth metals. 

In light atoms, N/Z=l. The nuclide for instance, has six protons and six neutrons in its nucleus. The combination of a pair of protons with a pair of neutrons has particularly high stability. That group corresponds to the stable helium nucleus, which also remains after some radioactive decays and is emitted as alpha (a) particles. When radium disintegrates, a particles are emitted. Electrons from the environment are added to the helium nuclei and neutral helium atoms are formed. That is the reason why helium was discovered in uraninite. 

In 1868, helium (He from Greek helios , the sun) was discovered due to a pale yellow line at 587.6 nm during the spectroanalytical examination of the solar prominences. In 1882, it was also detected in the spectral analysis of lava from the Vesuvius and as gas occlusion in the uranium mineral uraninite in 1889. Only in 1895, helium could be produced in its pure form in larger quantities from the mineral cleveite. And in 1908, H. Kamerlin -Onnes at Leiden succeeded for the first time in liquefying helium [4.1]. 

---