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
Uraninite Uraninite Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO, but due to oxidation the mineral typically contains variable proportions of UO. Additionally, due to radioactive decay, the ore also contains oxides of lead and trace amounts of helium. It may also contain thorium and rare earth elements. Uraninite used to be known as pitchblende (from "pitch", because of its black color, and "blende", a term (otherwise meaning "shade" or "screen") used by German miners to denote minerals whose density suggested metal content, but whose exploitation, at the time they were