Overview

During the late 1830s and early 1840s, Swedish chemist Carl Gustav Mosander (1797-1858) was studying two puzzling minerals, ceria and yttria. Both minerals had been discovered more than fifty years earlier in remote parts of Sweden. The minerals were puzzling because they seemed to consist of a mixture of new elements. Mosander eventually showed that one of the elements in ceria produced pink compounds. He called the new element didymium.

A few years after didymium was discovered, Austrian chemist Carl Auer (Baron von Welsbach) (1858-1929) made a correction to Mosander's research. Didymium was not a pure element, Auer announced, but a combination of two other new elements. He called these elements meodymium and praseodymium.