DISCOVERT OF NEW CHEMICAL ELEMENTS. 827 



gadolinite, and yttrotitanite. This metal, the oxide of which exists 

 only in quantities of a few grammes, and which no person, perhaps, 

 other than the author of the discovery has had in his hands, pos- 

 sesses considerable scientific importance, because its atomic weight 

 of 44, as determined by Mlson, is precisely that indicated by Men- 

 deleef for ekdbor, an element the existence of which was predicated 

 by the periodic law. 



In 1794, Gadolin had separated from the gadolinite of Ytterby 

 an earth which he called the earth of Ytter, and which was afterward 

 known under the forms of erbia, terbia, and yttria proper. These 

 earths were found in a considerable number of rare minerals, but the 

 oxides extracted from these minerals exhibited different natures 

 and aspects, presenting themselves rather like mixtures in which 

 the separation of the different constituents was attended by con- 

 siderable difficulties, for the different elements gave no very distinct 

 reaction. It was necessary to recur to spectrum analysis and to the 

 determination of atomic weights, and to try to isolate them by 

 repeated fractionings, under the action of sulphate of potassium 

 or of ammonia, or else by the partial decomposition of the nitrates 

 by heat. The bulk of these analyses, the results of which are not, 

 however, entirely clear as yet on some points, have been performed 

 within the last quarter of a century, and, besides securing more pre- 

 cise knowledge of scandium and yttrium, have revealed the exist- 

 ence of numerous other rare elements, the reduction of which 

 does not seem impossible; among which we cite erbium, holmium, 

 thulium, dysprosium, terbium, gadolinium, samarium, decipium, 

 and ytterbium. 



Cerium, lanthanum, and didymium have been the object re- 

 cently of very attentive researches having a practical end in view 

 the constitution of mantles for incandescent gaslights. Didymium 

 has been long suspected of not being a simple substance; but Carl 

 Auer von Welsbach, the inventor of this method of illumination, 

 is entitled to the credit of having succeeded, in 1855, in separating 

 didymium into its two elements of praesodidymium and neodi- 

 dymium. The utilization of monazite afterward permitted the prep- 

 aration of the salts of these remarkable metals in larger quantities, 

 and the practical use of them. 



The existence of metacerium, announced by M. Brauner, does 

 not yet appear to be fully established, nor that of russium, 

 which M. Crushchow has found associated with thorium in some 

 zircons and in monazite, and the atomic weight of which is cal- 

 culated at 220. The jargonium of Sorby, the austrium of Lin- 

 neman, the norvegium of Dahll, the actinium of Phipson, the 

 idumium of Websky, the masrium of Kichmond and Off, and 



