THE RARE-EARTH METALS

Abstract

Owing to the great similarity of the properties of the rare-earth elements in aqueous solutions, and to the fact that their precipitates in such media tend to form mixed crystals, it was a very tedious and time-consuming operation to separate the compounds of the elements in the pure form before ion-exchange techniques were developed. As a result, many scientists who would have liked to work with these elements found it extremely difficult and expensive to obtain them. Only a few workers who had specialized in this field were able to examine their properties. In spite of this difficulty, however, much of the inorganic chemistry of the rare earths was known by 1940. Cerium metal had been known for about 100 years, having been prepared by Mosander in 1827. In 1937, Klemm and Bommer had prepared the rare-earth metals in a form that permitted the determination of some of the properties of many of these metals, such as crystal structures, magnetic susceptibilities, and densities. This work indicated that the pure rare-earth elements in the metallic state were not nearly so much alike in their properties as had hitherto been generally assumed, and these differences became much more apparent as the metals were studied in more detail.