From the CRC handbook of Chemistry and Physics, CRC Press, Cleveland, 55th ed., 1974-75 "The Elements" by C.R. Hammond. page B-6
POLONIUM (Poland, native country of Mme. Curie), Po; at. mass. (~210); at. no. 84; m.p. 254 C; b.p. 962 C; sp.gr. (alpha modification) 9.32; valence -2,0,+2,+3(?),+4 and +6. Polonium was the first element discovered by Mme. Curie, in 1898, while seeking the cause of radioactivity of pitchblende from Joachimsthal, Bohemia. The electroscope showed it separated with bismuth. Polonium is also called Radium F. Polonium is a very rare natural element. Uranium ores contain only about 100 micrograms of the element per ton. Its abundance is only about 0.2% of that of radium. In 1934 it was found that when natural bismuth (Bi(209)) was bombarded by neutrons, Bi(210), the parent of polonium, was obtained. Milligram amounts of polonium may now be prepared this way, by using the high neutron fluxes of nuclear reactors. Polonium-210 is a low-melting, fairly volatie metal, 50% of which is vaporized in air in 45 housrs at 55 C. It is an alpha emitter with a half-life of 138.39 days. A milligram emits as many alpha particles as 5 grams of radium. The energy released by its decay is so large (27.5 calories per curie per day or 130 watts/gm.) that a capsule containing about half a gram reaches a temperature abouve 500 C. The capsule also presents a contact gammaray dose rate of 1.2 roentgen per hour. A few curies of polonium exhibit a blue glow, caused by excitation of the surronding gas. Because almost all alpha radiation is stopped within the solid source and its containter, giving up its energy, polonium has attracted attention for uses as light-wieight heat source for thermoelectric power in space satellites. Polonium has more isotopes than any other element. Twenty-seven isotopes of polonium are known, with atomic masses ranging from 192 to 218. Polonium-210 is the most readily available. Isotopes of mass 209 (half-life of 103 yrs.) and mass 208 (half-life 2.9 yrs.) can be prepared by alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron, but these are expensive to produce. Metallic polonium has been prepared from polonium hydroxde and somne other polonium compounds in the presence of concentrated aqueous or anhydrous liquid ammonia. Two allotropic modifications are know to exit. Polonium is readily dissovled in dilute acids, but is only slightly soluble in alkalis. Polonium salts of organic acids char rapidly; halide annines are reduced to the metal. Polonium can be mixed or alloyed with beryllium to provide a source of neutrons. It has been used in devices for eliminating static charges in textile mills, etc.; however, beta sources are more commonly used and are less dangerous. It is also used on brushes for removing dust from photographic films. The polonium for these is carefully sealed and controlled, minimizing hazards to the user. Polonium-209 is very dangerous to handle in even milligram or microgram amounts and special equipment and strict control is necessary. Damage arises from the complete absorption of the energy of the alpha particle into the tissue. The maximum permissilbe body-burden for ingesting polonium is only 0.03 micro curies, which represents a particle weighing only 6.8X10^12 grams. Weight-for-weight it is about 2.5X10^11 microcuries/cc. Polonium is availabel commercially on special order with an A.E.C. permit from the Oak Ridge National Laboratory.
