Radium seventh of a gram of radium. One kilogram of the Earth's crust contains about 900 picograms of radium, and one liter of sea water contains about 89 femtograms of radium. Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite (pitchblende) sample. While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive. They separated out an element similar to bismuth from pitchblende in July 1898, that turned out to be polonium. They then separated out a radioactive mixture consisting mostly of two
Radium bromide concentrate the radium as a combination of radium and barium. This is done by treating the ore with a barium salt and sulfuric acid which help the uranium, iron, copper, and other components become soluble. A residue containing gangue, barium, radium, and lead sulfates will be left over. The mixture will then be treated with sodium chloride to remove lead and convert radium and barium into carbonates that are insoluble in hydrochloric acid. The second step requires fractional crystallization to separate the barium from the radium. Because of the differences in solubility between radium and barium in bromide or chlorine,