The History of Praseodymium

From Wikipedia:

In 1839 Mosander extracted an oxide he called "lantana" (see lanthana), which was the oxide of the newly discovered element lanthanum, from a mixture of crude cerium nitrate. In 1841, Mosander went on to show that "lantana" was the most strongly basic of a mixture of rare earth element oxides and was the last to be precipitated from acid solution when base was added, or the first to be dissolved when the mixed oxides were leached with dilute acid. The remaining less-basic rare earth(s) retained the pinkish color, and Mosander called this remaining fraction "didymium." In 1874, Per Teodor Cleve concluded that didymium was in fact two elements, and in 1879, Lecoq de Boisbaudran isolated a new earth, samarium, from "didymium" obtained from the mineral samarskite. Crude didymium actually contained three elements, and in 1885, the Austrian chemist baron Carl Auer von Welsbach separated didymium into two elements, praseodymium and neodymium, which gave salts of different colors.

The name praseodymium comes from the Greek prasios (πράσιος), meaning green, and didymos (δίδυμος), twin. Praseodymium is frequently misspelled as praseodynium.
Leo Moser (son of Ludwig Moser, founder of the Moser Glassworks in what is now Karlovy Vary, Bohemia, in the Czech Republic, not to be confused with Leo Moser, a mathematician) investigated the use of praseodymium in glass coloration in the late 1920s. The result was a yellow-green glass given the name "Prasemit". However, a similar color could be achieved with colorants costing only a minute fraction of what praseodymium cost in the late 1920s, such that the color was not popular, few pieces were made, and examples are now extremely rare. Moser also blended praseodymium with neodymium to produce "Heliolite" glass ("Heliolit" in German), which was more widely accepted. The first enduring commercial use of purified praseodymium, which continues today, is in the form of a yellow-orange stain for ceramics, "Praseodymium Yellow", which is a solid-solution of praseodymium in the zirconium silicate (zircon) lattice. This stain has no hint of green in it. By contrast, at sufficiently high loadings, praseodymium glass is distinctly green, rather than pure yellow.
Using classical separation methods, praseodymium was always difficult to purify. Much less abundant than the lanthanum and neodymium from which it was being separated (cerium having long since been removed by redox chemistry), praseodymium ended up being dispersed among a large number of fractions, and the resulting yields of purified material were low. Praseodymium has historically been a rare earth whose supply has exceeded demand. This has occasionally led to its being offered more cheaply than the far more abundant neodymium. Unwanted as such, much praseodymium has been marketed as a mixture with lanthanum and cerium, or "LCP" for the first letters of each of the constituents, for use in replacing the traditional lanthanide mixtures that were inexpensively made from monazite or bastnäsite. LCP is what remains of such mixtures, after the desirable neodymium, and all the heavier, rarer and more valuable lanthanides have been removed, by solvent extraction. However, as technology progresses, it has been found that praseodymium can be incorporated into neodymium-iron-boron magnets, thereby extending the supply of the much in demand neodymium[citation needed]. So LC is starting to replace LCP as a result.
In the 1930's it was found (Beck) that praseodymium dioxide could be precipitated from KOH/NaOH eutectic melts, by oxidation by electrochemistry, or by sodium chlorate. This formed the basis of a small-scale laboratory purification method.

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