DISCOVERY OF NEW CHEMICAL ELEMENTS. 829 



previsions; but his triumph was destined to be still more com- 

 plete, for to gallium were afterward added scandium (ekaboron), 

 discovered by M. L. F. Nilson in 1875, and germanium (ekasilicon), 

 discovered by me in 1886. 



The discovery of germanium, predicted under the name of eka- 

 silicon by Mendeleef, bears a resemblance to the discovery of the 

 planet Neptune, the existence of which had been shown by the cal- 

 culations of Adams and Leverrier. That discovery was not due to 

 a concurrence of favorable circumstances or to a happy accident, but 

 was the result of researches inspired by theoretic previsions, and the 

 concordance between the predicted and the real properties was so 

 great that Mendeleef regarded the discovery of germanium as an im- 

 portant verification of the periodic law. On only one point — that 

 touching its formations in Nature — did germanium completely fail 

 expectations. The search for it would be more likely made as an 

 oxide in the rare minerals of the north, along with titanium and 

 zirconium, than as a sulphide accompanying similar compounds of 

 arsenic and antimony in gangues of silver-bearing minerals. This 

 fact, with the comparative rarity of its mineral, argyrodite, has con- 

 tributed no little to delaying the elucidation of its real character. 

 For myself, I was at first inclined to regard it as eka-antimony, while 

 Mendeleef, after my first incomplete communications, thought it was 

 ekacadmium. At the same time, M. von Richter expressed the con- 

 viction that germanium was nothing else than the long-expected eka- 

 silicon, a conclusion that was justified by the correspondence of 

 atomic weights. 



The success of the bold speculations of Mendeleef permits the 

 affirmation that the elaboration of the periodic system constitutes 

 a great forward step for science. In the course of only fifteen 

 years all the predictions of the Russian chemist have been con- 

 firmed. New elements have come to fill the vacant spaces in his 

 table, and there is every reason to hope that a like fulfillment awaits 

 the rest of the natural system. 



Yet the two elements last discovered, argon and helium, do 

 not seem to present any relation with the periodic system. The 

 physical properties of argon are very distinct; its characteristic 

 spectrum distinguishes it with great certainty from all other sub- 

 stances; but chemically the gas manifests an extraordinary indiffer- 

 ence, and it has not so far been possible to make it enter into the 

 usual compounds with other elements. This peculiarity, and the 

 impossibility of introducing a simple body of the molecular weight 

 of argon (39.88) into the periodic system, have given occasion to all 

 sorts of hypotheses concerning the gas; and the question of its rela- 

 tions has not yet been answered. 



