Everything about Praseodymium totally explained
» For other meanings of the abbreviation Pr, see PR. | left=
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Praseodymium (or /ˌpreɪsioʊˈdɪmiəm/) is a
chemical element that has the symbol
Pr and
atomic number 59.
Notable characteristics
Praseodymium is a soft silvery
metal in the
lanthanide group. 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, exposing more metal to
oxidation. For this reason, praseodymium should be stored under a light
mineral oil or sealed in glass.
Applications
Uses of praseodymium:
History
The name
praseodymium comes from the
Greek prasios, meaning green, and
didymos, twin. Praseodymium is frequently
misspelled as praseody
nium.
In
1841,
Mosander extracted the rare earth
didymium from
lanthana. In
1874,
Per Teodor Cleve concluded that didymium was in fact two elements, and in
1879,
Lecoq de Boisbaudran isolated a new earth,
samarium, from didymium obtained from the mineral
samarskite. In
1885, the
Austrian
chemist baron
Carl Auer von Welsbach separated didymium into two elements, praseodymium and
neodymium, which gave
salts of different
colors.
Leo Moser (not to be confused with
Leo Moser, a mathematician) investigated the use of praseodymium in glass coloration in the late 1920s. The result was a yellow-green glass given the name "Prasemit". However, a similar color could be achieved with colorants costing only a minute fraction of what praseodymium cost in the late 1920s, such that the color wasn't popular, few pieces were made, and examples are now extremely rare. Moser also blended praseodymium with neodymium to produce "Heliolite" glass ("Heliolit" in
German), which was more widely accepted. The first enduring commercial use of praseodymium, which continues today, is in the form of a yellow-orange stain for ceramics, "Praseodymium Yellow", which is a solid-solution of praseodymium in the
zirconium silicate (zircon) lattice. This stain has no hint of green in it. By contrast, at sufficiently high loadings, praseodymium glass is distinctly green, rather than pure yellow.
Praseodymium has historically been a rare earth whose supply has exceeded demand. Unwanted as such, much praseodymium has been marketed as a mixture with lanthanum and cerium, or "LCP" for the first letters of each of the constituents, for use in replacing the traditional lanthanide mixtures that were inexpensively made from monazite or bastnaesite. LCP is what remains of such mixtures, after the desirable neodymium, and all the heavier, rarer and more valuable lanthanides have been removed, by solvent extraction. However, as technology progresses, praseodymium has been found possible to incorporate into neodymium-iron-boron magnets, thereby extending the supply of the much in demand neodymium. So LC is starting to replace LCP as a result.
Occurrence
Praseodymium is available in small quantities in Earth’s crust (9.5
ppm). It is found in the rare earth minerals
monazite and
bastnasite, typically comprising about 5% of the lanthanides contained therein, and can be recovered from bastnasite or monazite by an
ion exchange process, or by counter-current solvent extraction.
Praseodymium also makes up about 5% of
misch metal.
Compounds
Praseodymium compounds include:
Fluorides: PrF2, PrF3, PrF4
Chlorides: PrCl3
Bromides: PrBr3, Pr2Br5
Iodides: PrI2, PrI3, Pr2I5
Oxides: PrO2, Pr2O3, Pr6O11
Sulfides: PrS, Pr2S3
Selenides: PrSe
Tellurides: PrTe, Pr2Te3
Nitrides: PrN
See also .
Isotopes
Naturally occurring praseodymium is composed of one stable isotope, 141Pr. Thirty-eight radioisotopes have been characterized with the most stable being 143Pr with a half-life of 13.57 days and 142Pr with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less than 5.985 hours and the majority of these have half-lives that are less than 33 seconds. This element also has six meta states with the most stable being 138mPr (t½ 2.12 hours), 142mPr (t½ 14.6 minutes) and 134mPr (t½ 11 minutes).
The isotopes of praseodymium range in atomic weight from 120.955 u (121Pr) to 158.955 u (159Pr). The primary decay mode before the stable isotope, 141Pr, is electron capture and the primary mode after is beta minus decay. The primary decay products before 141Pr are element 58 (cerium) isotopes and the primary products after are element 60 (neodymium) isotopes.
Precautions
Like all rare earths, praseodymium is of low to moderate toxicity. Praseodymium has no known biological role.
Further Information
Get more info on 'Praseodymium'.
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