Praseodymium history

Pr and Nd C. Auer von Welsbach (1885). First they were considered to be one element, didymium, but as Delafontaine suspected, it was not one single element. It appeared to consist of two quite similar elements. The Greek word didymos, meaning twin, from which the name didymium is derived, refers to this. Praseodymium was isolated first, with "Praseo-green referring to the green color of its salts. Then another one was isolated, which was the new one of the twin Neodymium (http // www.rsc.org/periodic-table/element/59/praseodymium history Weeks 1968)... 

The higher oxides where the oxygen to metal ratio x in the oxides is in the range of 1.5 to 2.0 are observed for cerium, praseodymium and terbium. These oxides exhibit fluorite-typed dioxides, which do not necessary mean x = 2.0 but usually the x value is slightly smaller than 2.0. Again, the composition of these oxides depends on the temperature, oxygen potential and physical state, besides their history of preparation and treatment [8-11]. 

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