776 



SCIENCE. 



[N. S. Vol. XVII. No. 437. 



samarium was questioned by de Boisbau- 

 dran and Demargay, as late as 1893, the 

 latter stated that no real proof of the com- 

 plexity of samarium had been offered. 

 What an exquisite illustration we have here 

 of Tyndall's dictum, 'Every system must 

 be plastic to the extent that the growth of 

 knowledge demands'; for, but a few years 

 have passed before Demarcay (1901) an- 

 nounces europium, with atomic weight of 

 151 (approximately), obtained by pro- 

 longed fractionation of the double magne- 

 sium-samarium nitrate. His observations 

 are reported as proved by reversal, absorp- 

 tion, spark and electric phosphorescent 

 spectra. The element appears to lie be- 

 tween samarium and gadolinium, with sev- 

 eral strong lines in the violet and ultra- 

 violet. 



In 1883 Crookes brought into considera- 

 tion phosphorescent spectra obtained in a 

 vacuum tube under the influence of an elec- 

 tric discharge. The year following Lecoq 

 de Boisbaudran obtained another method of 

 securing a phosphorescent spectrum. It is 

 in fact an inverse spectrum, nearly related 

 to that of Crookes, very delicate, being 

 greatly influenced by small amounts of 

 foreign bodies and other conditions. The 

 brilliancy of the bands thus obtained does 

 not depend tipon the proportion of the 

 active substance present. A small amount 

 of the body with much inert material gives 

 a bright spectrum, consequently it offered 

 little promise as a method for following 

 the process of fractionation. 



Up to this time holmia and thulia had 

 not been freed from the other earths. In 

 1886 de Boisbaudran showed that holmia 

 was composed of true holmium (162) and 

 dysprosium ( ? ) , adverted to, character- 

 ized by several bands, the one to which Sir 

 Wm. Crookes called especial attention be- 

 ing X 451.5. This Englishman later (1889) 

 subjected yttrimn salts to a great number 



of fractionations, several thousand, finding 

 the bands of the original material distrib- 

 uted among the different fract,jons. Prom 

 this work he assiuned that yttrium could 

 be split into a number of elementary sub- 

 stances, which he termed ' meta-elements, ' 

 naming one victorium after the lamented 

 queen. Without doubt Sir William Crookes 

 enunciated in this paper an important prin- 

 ciple in inorganic research, namely, what 

 may be termed ' partial cleavage ' ; that is, 

 the fractioning of a complex mixture of 

 elements may be pushed to an extreme with 

 one compound and the bodies appear ele- 

 mentary. On applying another method, 

 or the same method to another compound 

 of the assumed elementary substance, the 

 cleavage may be brought about in another 

 direction, and so on. The 'genesis. of the 

 elements' was the natural theory offered 

 by that master mind. It was strongly 

 combated in the main, however, by de Bois- 

 baudran, who showed that two of the bands 

 obtained, Za. and Zp, are not at all related 

 to yttria, as the former follows holmium 

 and the latter is identical with terbium. 

 He says, further: 'Perfectly pure yttria 

 gives no phosphorescent spectrum.' Den- 

 nis, the American worker on the element 

 in question, appears to agree with the 

 French chemist. 



It may be recalled that Delafontaine ex- 

 tracted samarium (his original decipium) 

 from Mosander's didymium. The theoret- 

 ical work referred to naturally gave rise 

 to the complexity of didymium, which has 

 an absorption spectrum characterized by a 

 number of well-defined bands. In fact, 

 Cleve made the prediction of the presence 

 of another element in lanthanum and didy- 

 mium in 1878. Carl Auer (von Welsbach), 

 in 1885, by prolonged fractional crystal- 

 lization of the double ammonium nitrate, 

 obtained from the pink solution green salts 

 of praseodidymium (140) and rose-red 



