Excerpt from The Rare Earths: Their Occurrence, Chemistry, and Technology During the thirty years which have elapsed since Dr. Auer's application of the rare earths to the production of artificial light, the incandescent mantle industry' has developed to an extent which gives it a prominent place among those chemical industries which may be considered essential to modern civilisation. This technical development has in turn assisted and stimulated the scientific examination of the elements of this group, with the result that ordered and accurate knowledge is beginning to replace the confused and uncertain data which had been collected by earlier workers in the field. These advances have served to emphasise the scientific interest and importance of the rare earth group, and the difficulty of bringing it into relation with the other elements. The relatively scant attention devoted to the study of this province of inorganic chemistry by teachers and students in England is probably due no less to the difficulty in classification, and the uncertainty with regard to the homogeneity and individuality of the various members of the family - an uncertainty by no means entirely removed even now - than to the fact that the very extensive literature on the subject is somewhat confused and difficult of access, especially to those unfamiliar with the French and German languages. The present work is intended to give a general but fairly comprehensive account of tho rare earth group. In accordance with general usage, the elements zirconium and thorium have been included, though these are now recognised as falling outside the limits of the rare earth group proper. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.