Lutetium

Lutetium (pronEng|ljuːˈtiːʃiəm) is a chemical element with the symbol Lu and atomic number 71. A silvery-white rare metal, lutetium is the heaviest member of the rare-earth group.Parker, Sybil P., ed. Dictionary of Scientific and Technical Terms. 3rd ed. New York: McGraw-Hill, 1984. ] One of its radioactive isotopes is used in nuclear technology to determine the age of meteorites.American Heritage. The American Heritage Science Dictionary. Boston: Houghton Mifflin, 2005.] Lutetium usually occurs in association with yttrium and is sometimes used in metal alloys and as a catalyst in various processes. A strict correlation between periodic table blocks and chemical series for neutral atoms would describe lutetium as a transition metal because it is in the d-block, but it is a lanthanide according to IUPAC. [ [http://www.iupac.org/reports/provisional/abstract04/connelly_310804.html IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004)] (online draft of an updated version of the "Red Book" IR 3-6)]

Characteristics and applications

Lutetium is a silvery white corrosion-resistant trivalent metal that is relatively stable in air. Lutetium is the heaviest and hardest of the rare earth elements.Lutetium has the highest melting point of any lanthanide, probably related to the lanthanide contraction.

This element is very expensive to obtain in useful quantities and therefore it has very few commercial uses. However, stable lutetium can be used as catalysts in petroleum cracking in refineries and can also be used in alkylation, hydrogenation, and polymerization applications.

Lutetium-176 (¹⁷⁶Lu) has been used to date the age of meteorites.

Lutetium aluminium garnet (Al₅Lu₃O₁₂) has been proposed for use as a lens material in high refractive index immersion lithography.

Lutetium-177 (¹⁷⁷Lu), when bound to Octreotate (a somatostatin analogue), is used experimentally in targeted radionuclide therapy for neuroendocrine tumours.

Cerium-doped lutetium oxyorthosilicate (LSO) is currently the preferred compound for detectors in positron emission tomography (PET.) [Thompson CJ. Instrumentation. In: Wahl RL,ed. Principles and Practice of Positron Emission Tomography. Philadelphia: Lippincott Williams and Wilkins, 2002:51.]

History

Lutetium (Latin "Lutetia" meaning Paris) was independently discovered in 1907 by French scientist Georges Urbain, [cite journal
title = Un nouvel élément, le lutécium, résultant du dédoublement de l'ytterbium de Marignac
journal = Comptes rendus
volume = 145
issue =
year = 1908
url = http://gallica.bnf.fr/ark:/12148/bpt6k3099v/f759.table
pages = 759–762
author = M. G. Urbain] Austrian mineralogist Baron Carl Auer von Welsbach, and American chemist Charles James. [ [http://acswebcontent.acs.org/landmarks/landmarks/rareearth/discovery.html Separation of Rare Earth Elements ] ] All of these men found lutetium as an impurity in the mineral ytterbia which was thought by Swiss chemist Jean Charles Galissard de Marignac (and most others) to consist entirely of the element ytterbium.

The separation of lutetium from Marignac's ytterbium was first described by Urbain and the naming honor therefore went to him. He chose the names neoytterbium (new ytterbium) and lutecium for the new element but neoytterbium was eventually reverted back to ytterbium and in 1949 the spelling of element 71 was changed to lutetium.

The dispute on the priority of the discovery is documented in two articles in which Urbain and von Welsbach accuse each other of publishing results influenced by the published research of the other. [cite journal
title = Die Zerlegung des Ytterbiums in seine Elemente
journal = Monatshefte für Chemie
volume = 29
issue = 2
year = 1908
doi = 10.1007/BF01558944
pages = 181–225
author = C. Auer v. Welsbach ] [cite journal
title = Lutetium und Neoytterbium oder Cassiopeium und Aldebaranium -- Erwiderung auf den Artikel des Herrn Auer v. Welsbach
year = 1909
journal = Monatshefte für Chemie
volume = 31
issue = 10
doi = 10.1007/BF01530262
author = G. Urbain ]

The Commission on Atomic Mass, which was responsible for the attribution of the names for the new elements, settled the disputed in 1909 by granting priority to Urbain and adopting his names as official ones. An obvious problem with this decision was that Urbain was one of the four members of the commission. [cite journal
title = Bericht des Internationalen Atomgewichts-Ausschusses für 1909
year = 1909
journal = Berichte der deutschen chemischen Gesellschaft
volume = 42
issue = 1
pages = 11 - 17
doi = 10.1007/BF01530262
author = F. W. Clarke, W. Ostwald, T. E. Thorpe, G. Urbain10.1002/cber.19090420104]

Welsbach proposed the names "cassiopium" for element 71 (after the constellation Cassiopeia) and aldebaranium for the new name of ytterbium but these naming proposals were rejected (although many German scientists in the 1950s called the element 71 cassiopium).

The irony of all this is that Charles James, who had modestly stayed out of the argument as to priority, worked on a much larger scale than the others, and undoubtedly possessed the largest supply of lutetium at the time.

As a result of the development of practical ion-exchange separation technology in 1954, lutetium oxide became commercially available in significant quantities for the first time shortly thereafter. In their January 20, 1959 price list, the Lindsay Chemical Division of American Potash and Chemical Corporation was offering lutetium oxide of 99% purity at 1200 dollars per pound, and 99.9% purity at 1500 dollars per pound - derived from South African "rock" monazite. The minimum order quantity was one gram, priced at $5.30 or $6.70, respectively. In modern times, the rare earth specialty sources have been pricing kilogram quantities of lutetium oxide at somewhat more than a dollar per gram.

Occurrence

Found with almost all other rare-earth metals but never by itself, lutetium is very difficult to separate from other elements. Consequently, it is also one of the most expensive metals, costing about six times as much as gold.

The principal commercially viable ore of lutetium is the rare earth phosphate mineral monazite: (Ce, La, etc.) PO₄ which contains 0.003% of the element. Pure lutetium metal has only relatively recently been isolated and is very difficult to prepare (thus it is one of the rarest and most expensive of the rare earth metals). It is separated from other rare earth elements by ion exchange and then obtained in the elemental form by reduction of anhydrous LuCl₃ or LuF₃ by either an alkali metal or alkaline earth metal.

Isotopes

Naturally occurring lutetium is composed of 1 stable isotope ¹⁷⁵Lu (97.41% natural abundance) and 1 long-lived beta-radioactive isotope ¹⁷⁶Lu with a half-life of 3.78×10¹⁰ years (2.59% natural abundance). The last one is used in the radiometric dating (see Lutetium-hafnium dating). 33 radioisotopes have been characterized, with the most stable being naturally occurring ¹⁷⁶Lu, and artificial isotopes ¹⁷⁴Lu with a half-life of 3.31 years, and ¹⁷³Lu with a half-life of 1.37 years. All of the remaining radioactive isotopes have half-lives that are less than 9 days, and the majority of these have half-lives that are less than a half an hour. This element also has 18 meta states, with the most stable being ^177mLu ("T"_½=160.4 days), ^174mLu ("T"_½=142 days) and ^178mLu (T_½=23.1 minutes).

The known isotopes of lutetium range in atomic weight from 149.973 (¹⁵⁰Lu) to 183.961 (¹⁸⁴Lu). The primary decay mode before the most abundant stable isotope, ¹⁷⁵Lu, is electron capture (with some alpha and positron emission), and the primary mode after is beta emission. The primary decay products before ¹⁷⁵Lu are element 70 (ytterbium) isotopes and the primary products after are element 72 (hafnium) isotopes.

Applications

Lutetium is very expensive (upwards of $100 per gram) to obtain in useful quantities and therefore it has very few commercial uses. Some commercial applications include:
* Use as a pure beta emitter, using lutetium which has been exposed to neutron activation. A tiny amount of lutetium is added as a dopant to gadolinium gallium garnet (GGG), which is used in magnetic bubble memory devices.
* Use as a catalyst in the petroleum industry, or in organic light-emitting diodes (OLEDs).
* Research into possible uses for targeted radiotherapy for the development of new cancer therapies.
* Cerium-doped lutetium orthosilicate (Lu₂SiO₅:Ce), known as LSO, is a scintillator used mainly for Positron Emission Tomography.

Compounds

Fluoride: LuF₃, Chloride: LuCl₃, Bromide: LuBr₃, Iodide: LuI₃, Oxide: Lu₂O₃, Sulfide: Lu₂S₃, Nitride: LuN

Intermetalic compounds:
*Lutetium aluminium garnet

"See also ."

Precautions

Like other rare-earth metals lutetium is regarded as having a low degree of toxicity but it and especially its compounds should be handled with care nonetheless. Metal dust of this element is a fire and explosion hazard. Lutetium plays no biological role in the human body but is thought to help stimulate metabolism.

Notes

References

*"Guide to the Elements - Revised Edition", Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
* [http://periodic.lanl.gov/elements/71.html Los Alamos National Laboratory's Chemistry Division: Periodic Table - Lutetium]

External links

* [http://www.webelements.com/webelements/elements/text/Lu/index.html WebElements.com - Lutetium] (also used as a reference)
* [http://education.jlab.org/itselemental/ele071.html It's Elemental - Lutetium]
* [http://www.pse-mendelejew.de/bilder/lu.jpgpure Lutetium >99,9% picture in the element collection from Heinrich Pniok]