Page "Helium" Paragraph 9

On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite ( a variety of uraninite with at least 10 % rare earth elements ) with mineral acids.

Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas liberated by sulfuric acid, he noticed a bright yellow line that matched the D < sub > 3 </ sub > line observed in the spectrum of the Sun.

These samples were identified as helium by Lockyer and British physicist William Crookes.

It was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight.

Helium was also isolated by the American geochemist William Francis Hillebrand prior to Ramsay's discovery when he noticed unusual spectral lines while testing a sample of the mineral uraninite.

Hillebrand, however, attributed the lines to nitrogen.

His letter of congratulations to Ramsay offers an interesting case of discovery and near-discovery in science.