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Europium - Sinha S.P.

Sinha S.P. Europium - Springer-Verlag, 1967. - 88 p.
Download (direct link): europium1967.djvu
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Chapter 7. Possible Uses and Applications of Europium..................135
Appendix....................................................................................................138
References..................................................................................................140
Subject Index............................................................................................159
Chapter 1
Introduction
The element number 63 of the periodic Table, europium, one of the fourteen elements classified as lanthanides, was discovered by Bois-baudran in 1892. The group of elements having atomic number (Z) 57—71 are usually classified as lanthanides and very often referred to as rare earths. In Table 1 the lanthanides are arranged in ascending order of Z The term rare earth not only embraces the lanthanides, but also
Table 1. The rare earth elements and their symbols
;omic 3. (Z) Element Symbol Atomic weight
57 Lanthanum La 138.92
58 Cerium Ce 140.13
59 Praseodymium Pr 140.92
60 Neodymium Nd 144.27
61 Promethium Pm [147]
62 Samarium Sm 150.35
63 Europium Eu 152.0
64 Gadolinium Gd 157.26
65 Terbium Tb 158.93
66 Dysprosium Dy 162.51
67 Holmium Ho 164.94
68 Erbium Er 167.27
69 Thulium Tm 168.94
70 Ytterbium Yb 173.04
71 Lutetium Lu 174.99
scandium (Z = 21) and yttrium (Z = 39). Although the earlier scientists have used the term “earth” to denote the element, in a strict sense it refers to the oxide. The name “rare earth” is both inaccurate and misleading in the sense that they are not really rare (see Table 4) and not earths but metals. We often hear people working in the field talking of the “lighter lanthanides” or the “cerium group” elements, and the “heavier lanthanides” or the “yttrium group” elements. According to this arbitrary classification, elements with Z = 57—63 are “light” lanthanides, and those with Z = 64—71 are “heavy” lanthanides.
1 Sinha, Europium
2
Introduction
Many other subgroupings, e.g. the “terbium group,” which includes elements gadolinium, terbium and dysprosium, exist.
Historically, the first rare earth specimen was found by K. A. Arrhenius near Ytterby in 1787. The Finnish Chemist, Johann Gadolin, in 1794, for the first time, successfully separated a new oxide from the mineral found by Arrhenius. This new oxide was named yttria by Ekeberg (1797). The mineral was named gadolinite. In 1803 another oxide, very similar to yttria, was discovered independently by Klaproth, and Berzelius and Hisinger. This new oxide was named ceria, and the mineral from which it was isolated was called cerite.
It was C. G. Mosander who gave definite proof of the complex nature of ceria and yttria. He successfully separated lanthana (Greek lanthanos means hidden) from ceria by thermal decomposition of a nitrate obtained by treating ceria with nitric acid. He also obtained another fraction from ceria which he called didymia. In 1843 he resolved the mineral yttria into three fractions: (1) the most basic one, yttria (white) (2) the least basic one, erbia (yellow) (3) the intermediate, terbia (pink). J. G. G. de Marignac isolated a colourless earth which he called ytterbia. Urbain in 1907 and von Welsbach in 1908 found ytterbium to be complex. The components which von Welsbach separated were named neoytterbium and lutecium by him. L. F. Nilson, whilst working with ytterbia obtained a white oxide, which he named scandia. This new oxide had a lower equivalent weight than ytterbia, and the properties of the new element derived from it corresponded with the predicted properties of Mendeleeff’s ekaboron. Later Cleve confirmed Nilson’s work. By the fractional crystallization of erbia and terbia Cleve obtained three fractions each of which possessed characteristic absorption spectra. The original erbia had a spectrum which was mainly the sum of the spectra of three components, erbia, holmia and thulia. The elements derived from these three components were called erbium, holmium and thulium respectively. Boisbaudran fractionated holmia into two portions. The absorption spectrum of one fraction had maxima at 6404 and 5363 A, which corresponded to the bands of holmia, attributed by Cleve, but the other fraction showed absorption maxima at 4515 and 7530 A. This fraction was thought to contain a new earth and the name dysprosia (difficult to obtain) was given to it.
Kruss, Nilson, Cleve, Thompson and Becquerel found that Mosander’s didymia gave an absorption spectrum of varying intensities depending on the source from which it was isolated, von Welsbach (1885) separated samaria, praseodymia and neodymia from didymia. These samples of neodymia and praseodymia were not spectroscopically pure, and Kruss and Nilson concluded that at least eight elements might be present.
Introduction
3
In 1886 Boisbaudran prepared gadolina, and Urbain (1905) obtained it in a high degree of purity. In 1883 Cleve made an extensive examination of samaria and prepared many of its salts. However, samaria, which Cleve thought to be a chemical individual, proved to be really complex. Boisbattdran (1892) found that when Cleve’s samaria was fractioned with ammonia, the least basic fractions differed from the other fractions in showing three new lines in their spark spectrum. He considered the new spark lines to be due to a new element, but could not establish its identity. In 1906 Demar£ay fractionally crystallized the double magnesium nitrate preparation of Cleve’s samaria and obtained a new earth in a fairly pure state. He identified it with Boisbaudran’s new element and called it europia. He further found that his original samaria was contaminated with gadolina.
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