Lutetium and Ytterbium

Urbain, whose name was mentioned in the first lines of this chapter, contributed greatly to the development of REEs chemistry. He perfected the methods of their separation, obtained some oxides in a very pure form (to prepare pure thulium he performed 15 000 recrystallizations), redetermined the atomic masses but could not succeed in discovering a new element himself. 

Only in 1907 did the scientist have a stroke of luck. Urbain proved that the old ytterbium of Marignac was a mixture of two elements. Urbain retained the name for one of them and, therefore, the real date of birth of ytterbium is 1907. He named the other element lutetium (in honour of the old name of Paris—Lutetia). 

It turned out that when G. Urbain was working with ytterbium , von Welsbach (who had debunked didymium) was performing a similar operation. Having splitted ytterbium , the Austrian chemist consigned this name to oblivion and named the constituents aldebaranium and cassiopeum borrowing the names from astronomy. 

Urbain s article had been published, however, several months earlier thus making him the discoverer of lutetium although in German scientific literature the name cassiopeum and the symbol Cp were used for a long time. Many scientists believed that Welsbach s results were more relia- 

Lutetium turned out to be the last natural REE and it ends the rare-earth series. Urbain was, however, of a different opinion. In 1911 he announced the discovery of a new element, celtium, placing it after lutetium in the periodic table. Later it became clear that the finding of celtium was in fact an experimental error. Urbain had interpreted its spectrum incorrectly the new lines in it were actually due to already known elements. 

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Ytterby, village in Sweden) Marignac in 1878 discovered a new component, which he called ytterbia, in the earth then known as erbia. In 1907, Urbain separated ytterbia into two components, which he called neoytterbia and lutecia. The elements in these earths are now known as ytterbium and lutetium, respectively. These elements are identical with aldebaranium and cassiopeium, discovered independently and at about the same time by von Welsbach. 

Some nut trees accumulate mineral elements. Hickory nut is notable as an accumulator of aluminum compounds (30) the ash of its leaves contains up to 37.5% of AI2O2, compared with only 0.032% of aluminum oxide in the ash of the Fnglish walnut s autumn leaves. As an accumulator of rare-earth elements, hickory greatly exceeds all other plants their leaves show up to 2296 ppm of rare earths (scandium, yttrium, lanthanum, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). The amounts of rare-earth elements found in parts of the hickory nut are kernels, at 5 ppm shells, at 7 ppm and shucks, at 17 ppm. The kernel of the Bra2d nut contains large amounts of barium in an insoluble form when the nut is eaten, barium dissolves in the hydrochloric acid of the stomach. 

These include the following 14 elements cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmi-um, erbium, thulium, ytterbium, and lutetium. 

The leach liquor is first treated with a DEHPA solution to extract the heavy lanthanides, leaving the light elements in the raffinate. The loaded reagent is then stripped first with l.Smoldm nitric acid to remove the elements from neodymium to terbium, followed by 6moldm acid to separate yttrium and remaining heavy elements. Ytterbium and lutetium are only partially removed hence, a final strip with stronger acid, as mentioned earlier, or with 10% alkali is required before organic phase recycle. The main product from this flow sheet was yttrium, and the yttrium nitrate product was further extracted with a quaternary amine to produce a 99.999% product. 

Of the remaining elements such as holmium, erbium, thulium ytterbium and lutetium it is unfortunately true that their relatively low abundance coupled with high cost has tended to preclude their use in applications outside of the laboratory. 

Moseley s work not only shed much fight on the periodic system and the relationships between known elements and the radioactive isotopes, but was also a great stimulus in the search for the few elements remaining undiscovered (11). One of the first chemists to utilize the new method was Professor Georges Urbain of Paris, who took his rare earth preparations to Oxford for examination. Moseley showed him the characteristic fines of erbium, thulium, ytterbium, and lutetium, and confirmed in a few days the conclusions which Professor Urbain had made after twenty years... 

Even more striking in the old tooth is the abundance of rare earths (dysprosium, holmium, erbium, thulium, ytterbium, and lutetium) and the elements tantalum, tungsten, gold, thorium, and uranium. Rare earth minerals are found in Scandinavia (in fact, many rare earth elements were discovered there), but what were they used for Did people prepare food with them Did they somehow get into the food chain ... 

Ytterbium and lutetium ionic complexes, derived from enantiopure substituted (R)-binaphthylamine ligands of the general formula [Li(THF) ][Ln[(f )C2oHi2(NR)2]2], have been investigated as catalysts for hydroamination/cyclization of several unsatu- rated amines CH2=CH(CH2) C(R2)CH2NH2 (n = 1 or 2). Complexes with isopropyl or cyclohexyl substituents on nitrogen atoms were found to be efficient catalysts for the formation of N-containing heterocycles under mild conditions with enantiomeric excesses up to 78%.124... 

Notice that Moseley had made a minor mistake in the atomic number determinations of both holmium and dysprosium. The atomic number of holmium is namely 67, and dysprosium has an atomic number of 66. It also appears that Moseley attached some credence to the investigation of Auer von Welsbach who had demonstrated the complexity of thulium in 1911 by splitting it into three components. Moseley had incorporated two of these components (Tml and Tmll) in his atomic number sequence. Moseley therefore ascribed Urbain s neo-ytterbium and lutetium too high an atomic number (in reality the atomic numbers of ytterbium and... 

The solubility of rare earth fluorides REF3 is very low, the pXsp ranges from 19 to 15 for lighter rare earth lanthanum, cerium, praseodymium, and neodymium to heavier rare earth ytterbium and lutetium, respectively. 

Nilson s analysis still did not solve this confusion. In 1907, French chemist Georges Urbain announced that Nilson s ytterbium was also a mixture of two new elements. Urbain called these elements ytterbium and lutetium. Marignac, Nilson, and Urbain are all given part of the credit for the discovery of ytterbium. 

The solubility of thulium, ytterbium and lutetium hydroxides in potassium hydroxide solutions showedthat lutetium hydroxide had the highest solubility when dissolved in 12.5 M-KOH. Potassium hydroxylterbate and potassium hydroxolutetate of compositions K[Ln(0H)4(H20)] were isolated. 

Purification of Ytterbium and Lutetium. One hundred grams of crude lutetium-ytterbium acetate dissolved in 133 ml. of boiling water was treated with 22.7 g. of sodium in 250 ml. of mercury and with 7 ml. of glacial acetic acid. The resulting amalgam gave a yield of pure ytterbium oxide of 73%. Treatment of a similar sample with 28.4 g. of sodium gave a yield of pure ytterbium(III) oxide of 93%. 

It would be a preferable situation if the demand for elements that are very abundant would control the REE market. Unfortunately, this is not the case. The most wanted elements at this time are neod3unium and dysprosium (Binnemans et al. 2013). Cerium, praseodymium, and the heavy REEs holmium, gadohnium, thulium, ytterbium and lutetium are produced in excess, and are stockpiled. 

This assignment in turn meant that such elements as ytterbium and lutetium were advanced by one place, so no vacant space was left at element 72. Moseley was unable to place Urbain s keltium, which eventually turned out to be the same as lutetium, discovered by Urbain a few years previously. When matters were resolved, after Moseley s early death, only one form of thuhum remained and ytterbium and lutetium were found to have atomic numbers of 70 and 71, respectively. This meant that there was a vacant gap at 72 for a new element between lutetium and tantalum, the element that would eventually be named hafnium. 

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