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How Is Lutetium Isolated or Purified?

Lutetium is a rare earth metal or lanthanide, one of a group of elements that are either uncommon in nature or difficult to isolate from other elements, or both. Lutetium is both scarce and difficult to isolate, making it the rarest of the rare earth elements. Even when it is isolated, lutetium is expensive and has few applications, so interest in this element is primarily scientific.
  1. Discovery of Lutetium

    • A Swedish officer named Carl Axel Arrhenius discovered an unusual dark rock in 1787, and turned it over to a friend of his named Johan Gadolin for chemical analysis. The rock was found to be made of a complex combination of elements called yttria. When yttria was chemically analyzed, several new elements were discovered. At first, ytterbium was thought to be one of these elements. However, in 1907, George Urbain was able to show that ytterbium actually contained another element, which he named lutecium. The spelling of this word was later changed to lutetium. Because another chemist named Auer Von Welsbach made the same discovery around the same time, both men are usually given the credit for finding lutetium.

    Lutetium

    • When lutetium was finally separated from ytterbium, it was found to have an atomic number of 71 and an atomic mass of 174.97 g.mol -1. Lutetium melts at 1,663 degrees Celsius and boils at 3,395 degrees Celsius. Lutetium is never found on its own in nature, but always in combination with other very similar rare earth elements. It is extremely difficult to isolate pure lutetium from the other elements with which it is found. Even the chemists who proved the existence of lutetium were not able to obtain it in a pure form, but as a compound called lutetium oxide. It is now possible to isolate pure lutetium, but it is still expensive and difficult.

    Isolation with Sodium or Potassium

    • To isolate a sample of pure lutetium, chemists generally begin with either lutetium chloride or lutetium fluoride. If sodium or potassium is added to the sample of lutetium chloride or fluoride, it will react with the lutetium compound and cause it to separate out, leaving pure lutetium behind. This is a soft metal of silver-white color. It is worth approximately $75 per gram, but it has few uses that would justify the expense. One of its only viable commercial uses is as a chemical catalyst used in petroleum refineries.

    Isolation With Alkali

    • A compound of lutetium fluoride or chloride can also be purified with an alkaline earth metal or alkali. The alkali will reduce the compound down to its component parts, leaving a sample of pure lutetium. This method is also both difficult and expensive. Iodine, mercury and silver are all more common than lutetium, but the combination of lutetium's rarity with the difficulty and expense of isolating it and its limited usefulness all serve to limit interest in this element.


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