From the CRC handbook of Chemistry and Physics, CRC Press, Cleveland, 55th ed., 1974-75 "The Elements" by C.R. Hammond. page B-6
PROMETHIUM (Prometheus, who, according to mythology, stole fire from heaven), Pm; at. no. 61; m.p. ~ 1080 C; b.p. 2460 C(?); sp.gt. ....; valence 3. In 1902 Branner predicted the existence of an element betwen neodymium and samarium, and this was confirmed by Moseley in 1914. In 1941, workers at Ohio State University irradiated neodymium and praseodymium with neutrons, deuterons, and alpha particles, resp., and produced several new radioactivities, which most likely were those of Element 61. Wu and Segre, and Bethe, in 1942, confirmed the formation; however, chemical proof of the production of Element 61 was lacking because of the difficulty in separating the rare-earths from each other at that time. In 1945, Marinsky, Glendenin, and Coryell made the first chemical identification by use of ion-exchange chromatography. Their work was done by fission of uranium and by neutron bombardment of neodymium. Searches for the element on earth have been completely fruitless, and it now appears that promethium is completely missing from the earths's crust. Promethium, however, has been identified in the spectrum of the star HR^463 in Andromeda. This element is being formed recently near the star's surface, for no known isotope of promethium has a half-life longer than 17.7 yrs. Thirteen isotopes of promethium, with atomic masses from 141 to 154, are now known. Promethium-147, with a half-life of 2.5 yrs., is the most generally useful. Promethium-145 is the longest lived, and has a specific activity of 940 curies per gram. It is a soft beta emitter; although no gamma rays are emitted, x-radiation can be generated when beta particles impinge on elements of high atomic number, and great care must be taken in handling it. Promethium salts luminesce in the dark with a ppale blue or greenish glow, due to their high radioactivity. Ion-exchange methods led to preparation of about 10g of promethium from atomic reactor fuel processing wastes in early 1963. Little is yet generally known about the properties of metallic promethium. Two or more allotropic modifications are thought to exist. The element has applications as a beta source for thickness gages, and can be absorbed by a phosphor to produce light. Light produced in this manner can be used for signs or signals that require depandable operation; it can be used as a nuclear-powered battery by capturing light in photocells which convert it into electric current. Such a battery, using Pm(147), would have a useful life of about 5 years. Promethium shows promise as a protable x-ray unit, and it may become useful as a heat source to provide auxiliary power for space probes and satellites. More than thirty promethium compounds have been prepared. Most are colored. Promethium-147 is available to A.E.C. licensees at a cost of about 50 cents per curie.
