Lutetium

Lutetium

Lutetium is a chemical element with the symbol Lu and atomic number 71. It is a silvery white metal which resists corrosion in dry, but not moist, air. It is the last element in the lanthanide series, and traditionally counted among the rare earths.

Lutetium was independently discovered in 1907 by French scientist Georges Urbain, Austrian mineralogist Baron Carl Auer von Welsbach, and American chemist Charles James. All of these men found lutetium as an impurity in the mineral ytterbia, which was previously thought to consist entirely of ytterbium. The dispute on the priority of the discovery occurred shortly after, with Urbain and von Welsbach accusing each other of publishing results influenced by the published research of the other; the naming honor went to Urbain as he published his results earlier. He chose the name lutecium for the new element but in 1949 the spelling of element 71 was changed to lutetium. In 1909, the priority was finally granted to Urbain and his names were adopted as official ones; however, the name cassiopeium (or later cassiopium) for element 71 proposed by von Welsbach was used by many German scientists until the 1950s.

Lutetium is not a particularly abundant element, though significantly more common than silver in the earth's crust; it has few specific uses. Lutetium-176 is a relatively abundant (2.5%) radioactive isotope with a half-life of about 38 billion years, and so used to determine the age of meteorites. Lutetium usually occurs in association with the element yttrium and is sometimes used in metal alloys and as a catalyst in various chemical reactions. 177Lu-DOTA-TATE is used for radionuclide therapy (see Nuclear medicine) on neuroendocrine tumours.

Occurrence and production


Found with almost all other rare-earth metals but never by itself, lutetium is very difficult to separate from other elements. The principal commercially viable ore of lutetium is the rare earth phosphate mineral monazite: (Ce,La,etc.)PO4 which contains 0.0001% of the element. The abundance of lutetium in the Earth crust is only about 0.5 mg/kg. The main mining areas are China, United States, Brazil, India, Sri Lanka and Australia. The world production of lutetium (in the form of oxide) is about 10 tonnes per year. Pure lutetium metal is very difficult to prepare. It is one of the rarest and most expensive of the rare earth metals with the price about US$10,000 per kilogram, or about one-fourth that of gold.

Crushed minerals are treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths. Thorium precipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate to convert rare earths into their insoluble oxalates. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO3. Several rare earth metals, including lutetium, are separated as a double salt with ammonium nitrate by crystallization. Lutetium is separated by ion exchange. In this process, rare-earth ions are sorbed onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin. Lutetium salts are then selectively washed out by suitable complexing agent. Lutetium metal is then obtained by reduction of anhydrous LuCl3 or LuF3 by either an alkali metal or alkaline earth metal.

Symbol		Lu
Atomic Number		71
Atomic Weight		174.967
Oxidation States		+3
Electronegativity, Pauling		1.3
State at RT		Solid, Metal
Melting Point, K		1936
Boiling Point, K		3668

Appearance and Characteristics

Harmful effects:

Lutetium is considered to be non toxic.

Characteristics:

• Lutetium is a silvery-white rare earth metal.
• The metal tarnishes slowly in air and burns at 150 oC to the oxide.
• It is the densest and hardest of the lanthanides.
• It is also one of the least abundant lanthanides, however it is still more abundant on earth than silver or gold.
• When present in compounds, lutetium exists usually in the trivalent state ,Lu3+. Most of its salts are colorless.

Uses of Lutetium

• Lutetium oxide is used to make catalysts for cracking hydrocarbons in the petrochemical industry.
• 177Lu is used in cancer therapy and because of its long half-life, 176Lu is used to date the age of meteorites.
• Lutetium oxyorthosilicate (LSO) is currently used in detectors in positron emission tomography (PET). This is a noninvasive medical scan that creates a three-dimensional image of the body’s cellular activity.