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 for living dial painters. The project also focused on collection of information and, in some cases, tissue samples from the radium dial painters. When the project ended in 1993, detailed information of 2,403 cases had been collected. This led to a book on the effects of radium on humans. The book suggests that radium-228 exposure is more harmful to health than exposure to radium-226. Radium-228 is more able to cause cancer of the bone as the shorter half life of the radon-220 product compared to radon-222 causes the daughter nuclides of radium-228 to deliver a greater dose of alpha radiation