Helium


Hellium, the lighter of the noble gases, was the first to be discovered. In fact, this element was first identified in the Sun rather than in the Earth. In 1868, during a solar eclipse in India, a spectrometer was used for the first time in the study of the chromosphere around the Sun. The chromosphere's spectrum, among other bright stripes, contain the hydrogen characteristic stripes and a yellow one that, at the time, was thought to be corresponding to sodium. The French astronomer Janssen decided to study the origin of that stripe and tried to reproduce the chromosphere's spectrum starting from ordinary light. He succeeded his purpose proving that the yellow stripe did not belong to sodium, but was probably the stripe of a new element.

Lockyer and Frankland confirmed Janssen's results and proved that the bright yellow stripe could not have an earthly origin. Frankland proposed the name "helium" after the Greek word "Helios" for Sun. This stripe was later detected in spectrums of many other stars and, in 1882, Palmieri observed it in gases erupting from Vesuvius.

The search for this new element in the Earth was not very productive until 1895, when Sir William Ramsay examined a gas produced by a Norwegian ore (cleveite) when treated with acids. In this gas spectrum the bright yellow stripe appeared, proving the existence of hellium on Earth.

Sir William Ramsay made this discovery after the work of Hillebrand, in 1888, that stated that the boiling of uraninite with diluted sulfuric acid produced considerable amounts of an inert gas. He proved that part of this gas was nitrogen, and since helium was not known at the time, he thought that it was only nitrogen. In a letter to Sir William Ramsay, after the discovery of the element, Hillebrand mentioned that he noticed some strange stripes not present in a pure nitrogen spectrum. He did not take this in to account, but only mentioned it to his assistant, loosing in this way the merit of the discovery.

The discovery of hellium in radioactive materials was not totally understood until the discovery of radium in 1898. Then, it was verified that helium was a stable product of the radioactive elements desintegration. This led some scientists to conclude that the hellium present in Earth had that origin. Some others thought that the origin of helium on Earth was a survival of the "primordial helium".