The 50 Years Following Mosander

Abstract

As we have seen in the previous chapter, the work of Mosander expanded the rare earth family from two (Ce, Y) to six (Ce, La, Di, Tb, Er, Y) members. In the following 30 years, however, the subject ran out of steam. Berzelius had died and the rise of organic chemistry eclipsed the popularity of inorganic chemistry. Moreover those rare earths most readily susceptible to the traditional methods of discovery by fractional precipitation and crystallisation had been identified. Further progress in this direction required the development of improved techniques and new concepts. Thus it is no accident that the next phase of rare earth discovery followed the introduction of spectral analysis by Bunsen and Kirchhoff in 1859, and evolution of the notion that elements could be organized in a logical fashion into predictable groups, as exemplified by Mendeleev’s periodic system of 1869 onwards. The former advance provided a powerful new tool for seeking and identifying potentially novel elements, while the latter gave an indication, albeit at the time an imperfect one, of the number of additional rare earths that might yet exist.