Encyclopædia Britannica, Ninth Edition/Niobium

NIOBIUM, a very rare chemical element which was discovered by H. Rose in 1846 as a component of the columbite of Bodenmais. In it, as also in tantalite, pyrochlore, yttro-tantalite, and a few other rare minerals, it is constantly associated with tantalum, which was discovered by Ekkeberg in 1802. Both metals, with vanadium, form a kind of appendage to the nitrogen group of elements. Like these they are capable of forming acid pentoxides and corresponding chlorides and oxychlorides. The oxychlorides and oxyfluorides, NbOCl₃ and NbOF₃, were originally thought by Rose to be peculiar (unmixed) chlorides and fluorides of niobium, until Blomstrand ascertained their true nature. The atomic weights of the two elements are Ta=182 and Nb=94.