praseodymium


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Related to praseodymium: neodymium

praseodymium

(prā'zēōdĭm`ēəm, –sēō–) [Gr., =green twin], metallic chemical element; symbol Pr; at. no. 59; at. wt. 140.90765; m.p. 931°C;; b.p. 3,512°C;; sp. gr. about 6.8; valence +3 or +4. Praseodymium is a soft, malleable, ductile, silver-yellow metal. It exhibits allotropyallotropy
[Gr.,=other form]. A chemical element is said to exhibit allotropy when it occurs in two or more forms in the same physical state; the forms are called allotropes.
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; the α-form (hexagonal crystalline structure) has the density given above, but the β-form (above 800°C;, body-centered cubic crystalline structure) is less dense. Praseodymium is a rare-earth metalrare-earth metals,
in chemistry, group of metals including those of the lanthanide series and actinide series and usually yttrium, sometimes scandium and thorium, and rarely zirconium. Promethium, which is not found in nature, is not usually considered a rare-earth metal.
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 of the lanthanide serieslanthanide series,
a series of metallic elements, included in the rare-earth metals, in Group 3 of the periodic table. Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series.
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 in Group 3 of the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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. When exposed to air it forms a green oxide that does not protect it from further oxidation. Although the pure metal may be prepared by reduction of the chloride, it has few commercial uses. A major use of the metal is in a pyrophoric alloy used in cigarette lighter flints, but it need not be purified for this application. Praseodymium compounds have many uses. The oxide is used in carbon electrodes for arc lighting. The salts are used to color enamels and glass. Didymium glass used in glassblower's goggles contains praseodymium; this glass absorbs the yellow sodium glare of light from the torch flame. The major commercial source of praseodymium is the rare-earth minerals monazitemonazite
, yellow to reddish-brown natural phosphate of the rare earths, mainly the cerium and lanthanum metals, usually with some thorium. Yttrium, calcium, iron, and silica are frequently present.
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 and bastnasite. Praseodymium was discovered in 1885 by C. A. Von WelsbachWelsbach, Carl Auer, Baron von
, 1858–1929, Austrian chemist. He discovered the rare earth elements neodymium and praseodymium (1885) and lutetium (c.1908, independently of the French chemist Georges Urbain). He is known also for the invention of the Welsbach mantle.
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, who separated Mosander's "didymium" into two components, the earths neodymia and praseodymia.

praseodymium

[‚prā·zē·ō′dim·ē·əm]
(chemistry)
A chemical element, symbol Pr, atomic number 59, atomic weight 140.9077; a metallic element of the rare-earth group.

praseodymium

a malleable ductile silvery-white element of the lanthanide series of metals. It occurs principally in monazite and bastnaesite and is used with other rare earths in carbon-arc lights and as a pigment in glass. Symbol: Pr; atomic no.: 59; atomic wt.: 140.90765; valency: 3; relative density: 6.773; melting pt.: 931°C; boiling pt.: 3520°C
References in periodicals archive ?
Thanks to its novel anisotropic structure and the catalytic activity of praseodymium, this UPr-PS Janus composite particle exhibits great application prospect in the field of oriented catalysis.
It can be seen from the Fig 6 and 7 that both e' and e" decrease with the increase of Praseodymium concentration.
The holes react with [H.sub.2]O or O[H.sup.-] to form hydroxyl radicals (*OH) and the electronhole separation process is improved because BSO sample transfers photoelectrons to Pr when praseodymium appears on BSO surface [22, 30].
praseodymium, and neodymium are more abundant and concentrated and
Many hybrid electric vehicles use nickel metal hydride batteries, which include rare earth elements--lanthanum, neodymium, praseodymium, and cerium--as well as non-rare earth elements--cobalt, nickel, manganese, and aluminum.
For the determination of total trace and rare earth elements like vanadium (V), rubidium (Rb), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), tin (Sn), antimony (Sb), cesium (Cs), barium (Ba), lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd); the powdered sediment samples were hard-pressed at 60-65 mPa to prepare bead and were analyzed by X-Ray Fluorescence Spectroscopy, employing a Rigaku RIX 1000 (Tokyo, Japan) XRF.
Molycorp is expected to provide Sumitomo with approximately 2,500 metric tons per year of cerium- and lanthanum-based products and 250 metric tons of didymium oxide (a combination of neodymium and praseodymium) per year from its current production facility at Mountain Pass, California.
First discovered in 1787, these metals - including yttrium, praseodymium, neodymium, europium, and gadolinium - are now used in color TVs, lasers, high-tech magnets, batteries, lenses, and critical defense applications.
The mixture contained 35.3% lanthanum oxide, 25.2% cerium oxide, 10.2% praseodymium oxide and 29.3% of several other contaminating minerals which were present in trace amounts.
In June 2009, it was reported that there is struggle between the United States, China and Japan over "rare earths," which include neodymium, samarium, and praseodymium, as well as ceramic superconductors and alternatives to those materials in the experimental stage.