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For glow in the dark paint.
(L. radius, ray) Radium was discovered in 1898 by Mme. Curie in the pitchblende or
uraninite of North Bohemia, where it occurs. There is about 1 g of radium in 7 tons of
pitchblende. The element was isolated in 1911 by Mme. Curie and Debierne by; the
electrolysis of a solution of pure radium chloride, employing a mercury cathode; on
distillation in an atmosphere of hydrogen this amalgam yielded the pure metal.
Originally, radium was obtained from the rich pitchblende ore found in Joachimsthal,
Bohemia. The carnotite sands of Colorado furnish some radium, but richer ores are found in
the Republic of Zaire and the Great Lake region of Canada. Radium is present in all
uranium minerals, and could be extracted, if desired, from the extensive wastes of uranium
processing. Large uranium deposits are located in Ontario, New Mexico, Utah, Australia,
Radium is obtained commercially as bromide and chloride; it is doubtful if any
appreciable stock of the isolated element now exists. The pure metal is brilliant white
when freshly prepared, but blackens on exposure to air, probably due to formation of the
nitride. It exhibits luminescence, as do its slats; it decomposes in water and is somewhat
more volatile than barium. It is a member of the alkaline-earth group of metals. Radium
imparts a carmine red color to a flame. Radium emits alpha, beta, and gamma rays and when
mixed with beryllium produce neutrons. One gram of 226Ra undergoes 3.7 x 1010 disintegrations per s. The curie is defined
as that amount of radioactivity which has the same disintegration rate as 1 g of 226Ra.
Twenty five isotopes are now known; radium 226, the common isotope, has a half-life of
One gram of radium produces about 0.0001 ml (stp) of emanation, or radon gas, per day.
This is purged from the radium and sealed in minute tubes, which are used in the treatment
of cancer and other diseases. Radium is used in the producing of self-luminous paints,
neutron sources, and in medicine for the treatment of disease. Some of the more recently
discovered radioisotopes, such as 60Co, are now being used in place of radium. Some of
these sources are much more powerful, and others are safer to use. Radium loses about 1%
of its activity in 25 years, being transformed into elements of lower atomic weight. Lead
is a final product of disintegration. Stored radium should be ventilated to prevent
build-up of radon.
Inhalation, injection, or body exposure to radium can cause cancer and other body
disorders. The maximum permissible border in the total body for 226Ra is 7400 becquerel.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.
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