A scheme of analysis for the ceric rare earths
The elements numbered 57 to 71 have presented a problem in analytical chemistry unparalleled by that of any other group since their discovery over the span of the nineteenth century. The striking similarities in chemical behavior of the fifteen elements comprising this series have almost completely baffled analysts in every attack, and it is only with the increased use of those newer methods, best described as being of a strictly physical nature, that much real progress has been achieved. Where time-honored classical wet methods have failed rather disappointingly, newer methods based upon the use of the spectrograph and similar instruments have given much promise to the chemist interested in these elements. It is unfortunate that such determination leaves much to be desired in the way of quantitative accuracy, although as an orientation of purity, spectrographic data are of prime importance to the analyst. The problem, then, is to develop a method for the separation and determination of the rare earth elements based upon wet method techniques rather than upon the use of the spectrometer of other physical measuring instruments. The attack on the rare earth group as a whole would present almost insuperable obstacles to the worker pressed for time, and therefore only the elements comprising the cerium group have been chosen as a subject for research undertaken. As commonly accepted, this series consists of lanthanum, cerium, praseodymium, neodymium, element 61, and samarium. Europium might also be included, but its nature is much that of a transition element between the cerium and yttrium groups. The cerium group has been chosen because of the ready availability of the various salts (except those of element 61, of course) and because of the rather wide occurrence of the member elements in such minerals as monazite. Had time been available, an additional reason might have been the relatively simple spectre in the carbon or copper arc of these first elements of the whole rare earth series. Since most promise has been shown by the use of organic reagents, the greater part of the work has been done in this direction. An attempt has been made to select a representative cross-section of organic compounds used under a variety of conditions. Principal results are set forth in Table III of the appendix.
Earths, Rare Analysis, Chemistry, Physical Sciences and Mathematics
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