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Marie Curie: Discovery of Radium, 1909

A Pure Compound

The next step, isolating pure compounds of the new elements, proved next to impossible. While radium chloride was obtained by repeated re-crystallization, it was not possible, despite a beginning sample of fifty kilograms, to isolate a pure polonium compound.

All attention was now centered on radium. A large-scale extraction in 1910 yielded sufficient amounts and led to isolation of radium metal and detailed examination of the element's properties. The atomic weight was found to be 225; its radioactive power is at least a million times greater than that of uranium, penetrating thick photographic plates. Radium is spontaneously and continuously luminous and heat producing

Radium was used in medicine to destroy cancerous tumors by implantation of a radium source directly in the tumor. It increasingly came to be regarded as an elixir and restorative, but consequential, toxic side effects became known. The health hazard, termed "radiation sickness," caused such treatments to be discontinued in the 1930s and safer substitutes such as cobalt-60 came into use.