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Pr
Pr at. wt. 140.907
at. no. 59
m.p. 931±4°C
b.p. 3212°C
sp. gr. 6.772 (a)
sp. gr. 6.64 (P)
valence 3 or 4.
| SHELL | K | L | M | N | O | P | Q |
| SUB SHELL | He | Neon | Argon | Krypton | Xenon | Radon | Eka-radon |
| 1s | 2s 2p | 3s 3p | 3d 4s 4p | 4d 5s 5p | 4f 5d 6s 6p | 5f 6d 7s 7p | |
| Praseodymium | 1s22s22p63s23p63d104s24p64d105s25p6 | 4f25d16s2 | |||||
| Symbol | 4K11/2 | ||||||
In 1841 Mosander extracted the rare earth didymia from lanthana; in 1879 Lecoq de Boisbaudran isolated a new earth, samaria, from didymia obtained from the mineral samarskite. Six years prior, Praseodymia and neodymia were separated from didymia as two other earths, which gave salts of different colors, in 1885 by von Welsbach. Prior to this, in 1841, Mosander extracted the rare earth didymia from lanthana, and in 1879 Lecoq de Boisbaudran isolated a new earth, samaria from didymia obtained from the mineral samarskite. As with other rare earths, compounds of these elements in solution have dis- tinctive sharp spectral absorption bands or lines, some of which are only a few Angstroms wide. The element occurs along with other rare-earth elements in a variety of minerals. Monazite and bastnasite are the two principal commercial sources of the rare-earth metals. Ionexchange and solvent extraction techniques have led to much easier isolation of the rare earths and the cost has dropped greatly in the past few years. Praseodymium can be prepared by several methods, such as by calcium reduction of the anhydrous chloride or fluoride. Misch metal, used in making cigarette lighters, contains about 5 % praseodyrnium metal. Praseo- dymium is soft, silvery, malleable, and ductile. It was pre- pared in relatively pure form in 1931. It is somewhat 'more resistant to corrosion in air than europium, lanthanum, cerium or neodymium, but it does develop a green oxide coating that spalls off, when exposed to air. As with other rare~earth metals it should be kept under a light mineral oil, or sealed in plastic. The rare~arth oxides, including Pr2O3, are among the most refractory substances known. Along with other rare earths, it is widely used as a core material for carbon arcs used by the motion picture industry for studio lighting and projection. Salts of praseodymium are used to color glasses and enamels; when mixed with certain other materials, praseodymium produces an intense and unusually clean yellow color in glass. Didymium glass, of which praseodymium is a component, is a colorant for welder's goggles. The metal (99 + % pure) is priced at about 801 per gram or $225/lb.
© 2001 F. Davies
Delphi O.E.M. Co.
All rights reserved
