[1][2] Much of his work focused on the rare earths, isolating and separating elements such as europium and gadolinium, and studying their spectra, their magnetic properties and their atomic masses.

[3] Urbain served in teaching positions at the Préparateur at the École de Physique et Chimie Industrielle (1894-1895), in Charles Friedel's organic chemistry laboratory (1832-1899), in the Faculté des Science P.C.N.

By taking advantage of the weights of rare earths, he was able to design procedures to separate light from heavy fractions, using magnesium and bismuth nitrates.

[5] Urbain discovered the element lutetium (atomic number 71) independently in 1907 when he demonstrated that Jean Charles Galissard de Marignac's ytterbia contained two substances.

[8][11][12] The dispute was officially settled in 1909 by the Commission on Atomic Mass, which granted priority to Urbain as the first to describe the separation of lutetium from ytterbium.

[15] As of 1919, Urbain had completed an extensive study of phosphorescence spectra, and demonstrated that trace impurities could dramatically alter results.

By introducing impurities into artificially prepared mixtures, he was able to duplicate the results reported by other researchers, again testing claims about possible new elements.