In June of 1885, the baron Von Welsbash announced, in the Academy of Sciences of Vienna, the separation of the didimia in two new rare-earths, through repeated fractionation of the ammonium didymium nitrate. He proposed the names praseodymia (green twin) and neodymia (new twin) for these new compounds. In spite of the skepticism of many chemists, Robert Bunsen, an old teacher of Welsbash, recognized the legitimacy of this separation. Nor neither the neodymia nor the praseodymia were decomposed in simpler oxides.