William Hillebrand. Portrait of William F. Hillebrand (1853-1925), American geochemist and discoverer of the presence of helium gas on Earth. In 1888 Hillebrand found that the mineral uraninite or pitchblende released an inert gas when heated with sulphuric acid. Hillebrand initially thought that this gas was nitrogen. Sir William Ramsay analysed the spectrum of the gas in 1895 and showed that it was helium, an element previously only detected in the Sun. In 1875 Hillebrand made the first pure sample of the metal cerium by electrolysis of the mineral fused cerous chloride.
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