Radium of radium Curie used the residues after extraction of uranium from pitchblende. The uranium had been extracted by dissolution in sulfuric acid leaving radium sulfate, which is similar to barium sulfate but even less soluble in the residues. The residues also contained rather substantial amounts of barium sulfate which thus acted as a carrier for the radium sulfate. The first steps of the radium extraction process involved boiling with sodium hydroxide followed by hydrochloric acid treatment to remove as much as possible of other compounds. The remaining residue was then treated with sodium carbonate to convert the barium sulfate into
Radium Girls a two-year statute of limitations, but settled out of court in 1928. Five women in Illinois who were employees of the Radium Dial Company (which was unaffiliated with the United States Radium Corporation) sued their employer under Illinois law, winning damages in 1938. From 1917 to 1926, U.S. Radium Corporation, originally called the Radium Luminous Material Corporation, was engaged in the extraction and purification of radium from carnotite ore to produce luminous paints, which were marketed under the brand name "Undark". The ore was mined from the Paradox Valley in Colorado and other "Undark mines" in Utah. As a defense