Discovery
In 1841, the Swedish doctor and chemist Carl Gustav Mosander discovered the “new element Didymium” (from the Greek δίδυμος — twin), with properties that were very similar to lanthanum – hence the name of the element. Scientists at the time believed that didymium was a mixture of two or more elements. In 1885, the Austrian chemist Carl Auer von Welsbach dissolved double ammonium nitrates of didymium in nitric acid, and then carried out fractional crystallization. It turned out that didymium really was a mixture of two new elements. One of these elements formed bright green oxides. The scientist called this element “praseodymium” (from the Greek πράσιος, light green and δίδυμος, twin). The second element was neodymium (from the Greek νέος, new and δίδυμος, twin). A pure sample of praseodymium metal itself was first produced in 1931.
Uses
Praseodymium resembles the typical trivalent rare earths, however, it will exhibit a +4 state when stabilized in a zirconia host. The element is found in most all light rare earth derivatives.
It is highly valued for ceramics as a bright yellow pigment in praseodymium doped zirconia because of its optimum reflectance at 560 nm.
Much research is being done on its optical properties for use in amplification of telecommunication systems, including as a doping agent in Fluoride fibers.
Praseodymium is present in the rare earth mixture whose Fluoride forms the core of carbon arc lights which are used in the motion picture industry for studio lighting and projector lights.
Doping Praseodymium in Fluoride glass allows it to be used as a single mode fiber optical amplifier.
It is also used in the scintillator for medical CAT scans.
As an alloying agent with Magnesium to create high-strength metals that are used in aircraft engines.
Praseodymium compounds give glasses and enamels a yellow color.
Praseodymium Metal, is used as high-strength alloying agent in the Magnesium used in parts of aircraft engines. It is an important alloying agent in Neodymium-Iron-Boron magnets. Praseodymium is used to create high-power magnets notable for their strength and durability. It also used in lighters, torch strikers, 'flint and steel' fire starters, etc.
Chemical Properties
grey powder
Physical properties
Praseodymium is a silvery-white, soft metal that is easily formed into various shapes. Whenthe pure metal is exposed to the air, a green oxide coating forms on its surface. To preventoxidation, praseodymium is usually kept in oil in a covered container.
Its melting point is 931°C, its boiling point is 3,520°C, and its density is 6.77g/cm
3.
Isotopes
There are 45 isotopes of praseodymium. All are artificially produced and radioactivewith half-lives ranging from several hundred nanoseconds to 23.6 days. Only oneis stable (Pa-141), and it makes up 100% of the praseodymium found in the Earth’scrust.
Origin of Name
The name is derived from two Greek words, prasios and didymos,
which together mean “green twins.”
Occurrence
Praseodymium is the 41st most abundant element on Earth and is found in the ores of monazite,cerite, bastnasite, and allanite along with other rare-earths. Praseodymium is also the stableisotope resulting from the process of fission of some other heavy elements, such as uranium.
Praseodymium is mainly found in monazite sands and bastnasite ores. The monazite sandscontain all of the rare-earths and are found in river sand in India and Brazil as well as inFlorida beach sand. A large deposit of bastnasite exists in California.
Praseodymium is separated from its ore and other rare-earths by a process called ionexchange, which exchanges one type of ion for another.
Characteristics
As a metal, Pr is hygroscopic (adsorbs water) and tarnishes in the atmosphere. It will reactwith water to liberate hydrogen. It is soluble in acids and forms greenish salts, along with someother rare-earths. It is used to fabricate the electrodes for high-intensity lights.
History
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. Praseodymium 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. Ion-exchange and solvent extraction
techniques have led to much easier isolation of the rare earths
and the cost has dropped greatly. Thirty-seven isotopes and
isomers are now recognized. 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% praseodymium metal.
Praseodymium is soft, silvery, malleable, and ductile. It was
prepared 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 splits 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-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.
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 (99.9% pure)
is priced at about $4/g.
Uses
Praseodymium’s major use is as an alloying agent along with magnesium to produce highstrengthsteel that is used in airplane engines and automobiles parts. Notwithstanding its greenish color, another important use of praseodymium is as a yellow pigment to color glassand ceramics. Along with several other rare-earths, it is also used to form the electrodes forhigh-intensity arc lamps.
It is used to manufacture safety goggles that filter out strong yellow light (used in welding,for example). Misch metal uses about 5% Pr in the manufacture of cigarette lighter flints.
Uses
Praseodymium optical properties for use in amplification of telecommunication systems, including as a doping agent in fluoride fibers. It is also used in the scintillator for medical CAT scans. Used as additive for special steel, non-ferric alloy, hydrogen storage alloy, also reducer for making other rare Earth metal.
Uses
Praseodymium salts, ingredient of mischmetal,
core material for carbon arcs, colorant in glazes and
glasses, catalyst, phosphors, lasers.
Definition
Pr. Metallic element of atomic
number 59, group IIIB of the periodic table, one of the rare earth elements of the lanthanide group, aw
140.9077, valences = 3, 4. No stable isotopes.
Definition
praseodymium: Symbol Pr. A softsilvery metallic element belonging tothe lanthanoids; a.n. 59; r.a.m.140.91; r.d. 6.773; m.p. 931°C; b.p.3512°C. It occurs in bastnasite andmonazite, from which it is recoveredby an ion-exchange process. The onlynaturally occurring isotope ispraseodymium–141, which is notradioactive; however, fourteen radioisotopeshave been produced. It isused in mischmetal, a rare-earthalloy containing 5% praseodymium,for use in lighter ints. Another rareearthmixture containing 30%praseodymium is used as a catalyst in cracking crude oil. The element wasdiscovered by C. A. von Welsbach in1885.
Preparation
Praesodymium may be recovered from its minerals monazite and bastanasite. The didymia extract of rare earth minerals is a mixture of praesodymia and neodymia, primarily oxides of praesodymium and neodymium. Several methods are known for isolation of rare earths. These are applicable to all rare earths including praesodymium. They include solvent extractions,ionexchange, and fractional crystallization. While the first two methods form easy and rapid separation of rare earth metals, fractional crystallization is more tedious. Extractions and separations of rare earths have been discussed in detail earlier (see Neodymium and Cerium).
Praesodymium metal can be obtained from its anhydrous halides by reduction with calcium. The metal also may be prepared by electrolysis of fused praesodymium chloride at elevated temperatures (about 1,000°C).Alternatively, an eutectic mixture of praesodymium chloride, potassium chloride, and sodium chloride may be electrolyzed. In such electrolysis graphite is the anode and tungsten the cathode.
Definition
A soft ductile malleable silvery element of
the lanthanoid series of metals. It occurs in
association with other lanthanoids.
Praseodymium is used in several alloys, as
a catalyst, and in enamel and yellow glass
for eye protection.
Symbol: Pr; m.p. 931°C; b.p. 3512°C;
r.d. 6.773 (20°C); p.n. 59; r.a.m. 140.91.
Hazard
If praseodymium gets wet or is submerged in water, the hydrogen released may explode. Itmust be kept dry and protected from the atmosphere.
