Praseodymium

At A Glance: Pr

Atomic Number: 59
Atomic Symbol: Pr
Atomic Weight: 140.9077
Electron Configuration: [Xe]6s24f3
Atomic Radius: 239 pm (Van der Waals)
Melting Point: 931 °C
Boiling Point: 3520 °C
Oxidation States: 3
Sources: Monazite and bastnasite are the two principal commercial sources of praseodymium.Uses: Paired with neodymium in permanent magnets, also used in photographic filters, airport signal lenses, pigment in ceramic tile and glass, pollution control catalysts.Content provided by Los Alamos National Laboratory. Used with permission.

Rare earth elements - Praseodymium
Rare earth elements - Praseodymium
Praseodymium Spin Video

Photos of rare earth elements used on our site are copyright of Max Whitby and Theodore Gray. Used with permission.

Praseodymium, just 4% of the Lanthanide content of Bastnasite, is a common coloring pigment. Along with Neodymium, Praseodymium is used to filter certain wavelengths of light. Praseodymium is used in photographic filters, airport signal lenses, and welder’s glasses. Its color allows production of various pigments used in coloring products such as ceramic tile and glass. Vibrant yellow ceramic tiles and glasses most likely contain Praseodymium and certain premium quality mirrors and lenses also depend on Praseodymium.

As part of an alloy, Praseodymium is used in permanent magnet systems designed to make smaller and lighter motors. Praseodymium is also used in automobile and other internal combustion engine pollution control catalysts.

Misch metal, used in making cigarette lighters, contains about 5% praseodymium metal. The rare-earth 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.

History

From the Greek word prasios, green, and didymos, twin. 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 later, in 1885, von Welsbach separated didymia into two others, praseodymia and neodymia, which gave salts of different colors. As with other rare earths, compounds of these elements in solution have distinctive sharp spectral absorption bands or lines, some of which are only a few Angstroms wide.

Sources

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. It was prepared in relatively pure form in 1931.

Production

Ion-exchange 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 of fluoride.

Properties

Praseodymium is soft, silvery, malleable, and ductile. It is somewhat more resistant to corrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that falls off when exposed to air. As with other rare-earth metals, it should be kept under a light mineral oil or sealed in plastic.

Sources: Los Alamos National Laboratory; Molycorp

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