On the phosphorescent spectra of Sδ and Europium

Abstract

The recent examination of a pure specimen of europium prepared by M. Urbain has brought to light some interesting facts connected with its phosphorescent spectrum when the sulphate is subjected to cathode radiations in a radiant matter tube. In Demartcay’s paper announcing the discovery of europium, he referred to the phosphorescent spectrum of the new earth in the following terms:— “In 1885 Sir William Crookes, during his beautiful researches on electric phosphorescence in vacuo , noticed a band which he attributed to samarium, and which, by reason of its disappearance in the presence of lime and from certain other peculiarities, he called the ‘anomalous line.’ Later he distin­guished this, together with a large number of other bands, as belonging each to a special meta-element. The hypothetical meta-element corresponding to the anomalous line he called Sδ. M. Lecoq de Boisbaudran, in the course of his important researches on phosphorescence, confirmed the above statements with regard to this anomalous line. In 1892 M. de Boisbaudran described a spectrum consisting of three brilliant blue lines discovered in the spark spectrum of samarium. He concluded that they corresponded to a particular element, Zε. About the same time he also drew attention to a particular band in the reversal spectrum of samarium, which apparently corresponded to the anomalous line. M. de Boisbaudran, without forming very precise conclusions, inclined to the idea that this line was due to a particular element, Zζ. In1896 I discovered the presence of an element intermediate between gadolinium and samarium. In1900 I showed that this new element was identical with de Boisbaudran’s Zε, and that Crookes’s anomalous band was due to the same substance, as well as the reversal line Zζ . . . Since that period, by a long series of fractionations with magnesium nitrate, I have been able to accumulate a considerable quantity of this element. The apparently contradictory results of Crookes and de Boisbaudran are due, I think, to the very small proportions of Z—Zε contained in their material. I propose the name Europium for the new element, with symbol Eu, and atomic weight 151 (approx.)”