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The light effect is, however, considerably increased by the use of phosphorescent bodies such as yttria, uranium glass, etc.

In 1797 Ekeberg showed that gadolinite contained another rare earth, which was given the name yttria.

Yttria is an exceedingly complex mixture, which has been decomposed, yielding as an intermediate product terbia.

By such a study in the ultra-violet region of a fraction prepared from crude yttria he detected a new element victorium, and subsequently by elaborate fractionation obtained the element itself.

These crude earths, yttria and ceria, have supplied most if not all of the “rare earth” metals.