The Ra-226 isotope was discovered and prepared by Marie Curie. This isotope has been applied to the study of the general properties of radioactivity and radiation. Ra-226 has been prepared by coprecipitation with very insoluble lead and barium salts. The coprecipitate has been purified by fractionated crystallization. Metallic radium has been produced by the electrolysis of molten salt in 1910.

The Ra-226 isotope has been used in cancer therapy. Radium is contained in metallic needles, and these needles are implanted next to the tumor. The disadvan­tage of the application of radium is that it is very toxic; the lethal dose is 1 pg. Any damage of the needle containing radium could cause death.