II.

Properties and Occurrence

Radium-226 metal melts at about 700°C (about 1292°F) and has a specific gravity of 5. The element oxidizes immediately upon exposure to air. The element is used and handled in the form of radium chloride or radium bromide and practically never in the metallic state.

Radium is formed by the radioactive disintegration of uranium and is consequently found in all uranium ores. Radium is present in uranium ore to the extent of 1 part of radium to 3 million of uranium. It is extracted from the ore by the addition of a compound of barium that acts as a “carrier.” The chemical properties of radium are similar to those of barium, and the two substances are removed from the other components of the ore by precipitation of barium and radium sulfate. The sulfates are converted into carbonates or sulfides, which are then dissolved in hydrochloric acid. The radium is separated from the barium as the end result of successive crystallizations of the chloride solutions.

Of the isotopes of radium, ranging in mass number from 202 to 234, the most abundant and most stable is the isotope of mass 226. Radium-226 is formed by the radioactive disintegration of the thorium isotope of mass 230, which is the fourth successive isotope in the decay series starting with uranium-238. The half-life of radium-226 is 1599 years. It emits alpha particles, forming the gas radon.