ABSTRACT
In two recent communications to the Paris Academy of Sciences Comptes rendus, May 22, by M. A. Dauvillier and G. Urbain respectively, very definite conclusions have been reached as to the identity of celtium with the missing element of number 72 on the Moseley classification. This chapter presents a translation of Urbain's paper in the Comptes rendus. The results of Dauvillier's examination of Urbain's preparations containing celtium have a theoretical importance for those who have followed recent scientific developments with regard to the chemical elements and their atomic structure. It is unquestionable that the element of atomic number 72 is actually celtium. The atomic weight of celtium must therefore lie between 175 (lutecium) and 181.5 (tantalum). Though Urbain only succeeded in obtaining a partial separation, this was sufficient to permit the high-frequency spectra method to assign its atomic number to each of the constituents he discovered, namely (neo-) ytterbium 70, lutecium 71, celtium 72.
