Didymium separation

Naturally, Brauner did not obtain pentavalent didymium . We know now that lanthanides cannot reach this oxidation state. However, trying to determine the atomic mass of didymium more correctly, Brauner decided to obtain the element in as pure a form as possible. He discovered that didymium separated from samarium could be divided into three fractions somewhat differing in molecular weights. Brauner performed this experiment in 1883 but he had to stop further research for some reasons. It was a great pity since he was so close to ending the story of the old didymium . 

Gr. neos, new, and didymos, twin) In 1841, Mosander, extracted from cerite a new rose-colored oxide, which he believed contained a new element. He named the element didymium, as it was an inseparable twin brother of lanthanum. In 1885 von Welsbach separated didymium into two new elemental components, neodymia and praseodymia, by repeated fractionation of ammonium didymium nitrate. While the free metal is in misch metal, long known and used as a pyrophoric alloy for light flints, the element was not isolated in relatively pure form until 1925. Neodymium is present in misch metal to the extent of about 18%. It is present in the minerals monazite and bastnasite, which are principal sources of rare-earth metals. 

Lanthanum - the atomic number is 57 and the chemical symbol is La. The name derives from the Greek lanthanein for to be hidden or to escape notice because it hid in cerium ore and was difficult to separate from that rare earth mineral. It was discovered by the Swedish surgeon and chemist Carl-Gustav Mosander in 1839. In 1842, Mosander separated his lanthanium sample into two oxides for one of these he retained the name lanthanum and for the other he gave the name didymium (or twin). 

Neodymium - the atomic number is 60 and the chemical symbol is Nd. The name was originally neodidymium and was later shortened to neodymium, which is derived from the Greek neos for new and didymos for twin . It was discovered by the Swedish surgeon and chemist Carl Gustav Mosander in 1841, who called it didymium (or twin) because of its similarity to lanthanium which he had previously discovered two years earlier. In 1885, the Austrian chemist Carl Auer von Welsbach separated didymium into two elements. One of which he called neodymium (or new twin). 

In 1885 Carl Auer Baron von Welsbach (1858-1929) separated the oxides of two similar elements from didymium. He named one praseodymium from the Greek word prasios, which means green or the green twin, and he named the other element neodymium, which is derived from new and dymium and means new twin. ... 

In 1885 Carl Auer Baron van Welsbach separated a common rare-earth called didymium into two distinct rare-earths. One he called green didymia (praseodymium) and the other he named new didymia (neodymium). The green color of green didymia (praseodymium) is caused by contamination of iron. 

Marignac, Lecoq de Boisbaudran, Cleve, and Bohuslav Brauner all believed didymium to be a mixture of elements, but none of them were able to make the difficult separation (49). In 1882 Professor Brauner of the University of Prague examined some of his didymia fractions with the spectroscope and found a group of absorption bands in the blue region (A=449-443) and another in the yellow (A.=590-568) (53, 66)." These two groups of bands are now known to belong to two earths, praseodymia and neodymia, respectively, which Baron Auer von Welsbach obtained in 1885 by splitting didymia (3, 30, 32, 58). 

Yet that was not the end of it. Other chemists suspected that didymium too was not a pure element, but a mixture. Separating its components chemically was very difficult, as they seemed to behave almost identically. But their presence was revealed by inspecting the bar code of elemental emission lines in the glow produced when the material was heated. 

F. T. Freriehs and E. F. Smith obtained didymium nitrite in aq. soln. as a dark brown viscid liquid. G. Kriiss and A. Loose attempted to prepare yttrium and cerium nitrites and to use the result as a means of separation of the earths. 

During the course of the 19th century the number of known elements increased greatly. It happened that substances which were first considered to be elements were later found to be further divisible. Thus Lavoisier still considered calcium oxide, CaO, as an element and in the Rare Earth Group the element55 didymium was only separated into neodymium and praseodymium as late as 1885. 

A fraction of Ce, La. Nd and Pr derived from bastnasite or monazite is a typical feedstock in the recovery process of cerium on a commercial scale. Separation of the rare-earth elements may be achieved by splitting the mixed rare-earth elements into a cerium/lanthanum and didymium (Nd/Pr) fraction first. The cerium/lanthanum fraction may be used as a further feedstock in a second extraction stage and will yield high pure cerium and lanthanum solution respectively. Cerium can then be precipitated as. for example, an oxalate or a carbonate which may be used as precursor for cerium derivatives. 

Cerite was thoroughly studied by Swedish chemist Carl Gustav Mosander (1797-1858). In 1839, Mosander was able to separate cerite into two parts, which he called cerium and lanthanum. Mosander believed he had found two new elements. Two years later, however, he learned that his lanthanum was not an element but a mixture of two parts. Mosander called these two new parts lanthanum and didymium. Mosander chose the name didymium because it means twin. He said that didymium was like an identical twin to lanthanum. Chemists later confirmed that two of Mosander s discoveries were really new elements cerium and lanthanum. 

At nearly the same time, French chemist Jean-Charles-Galissard de Marignac (1817—1894) was also studying didymium. fie was able to separate didymium into two parts, which he called didymium and samarium. He announced that samarium was a new element. 

Nd neodymium, 60, 1885 from the Greek "neo (new) and didymos (twin) neodymium and praseodymium were separated from a material once called didymium and thought to be a single element similar to lanthanum. 

Neisch, A. C. A New Separation of Thorium from Cerium, Lanthanum and Didymium by Meta-nitroben-zoic acid. 

Thus, Mosander s activities led to the originally two-element division into a six-element division. The cerium compounds are yellow at the higher oxidation level and colourless at the lower oxidation level, lanthanum compounds are white, didymium compounds are red, yttrium and erbium compounds are white, terbium compounds are pink. Chemists existed, of course, who disputed the existence of these elements. Unequivocal identification of elements was, however, possible in later times only. In the period in question, the main characteristics on the basis of which a substance could be qualified as a new element were separability, colour, crystal shape and reactivity. Even atomic mass determinations were largely uncertain, particularly in the group of the rare earth elements, it will be seen in the... 

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