THE DISCOVERY OF NEW ELEMENTS. 241 



very small proportion of the new metal. This proportion is not, in fact, 

 more than a ten-thonsandth per cent, while the richer blende of Bern- 

 bryer contains a thousandth. The preparation of any considerable 

 qnantities of gallium Avas naturally attended with great diflticulties 

 because there was no ore known from which it could be obtained, and 

 yet the study of the new mineral is of the greatest interest because of 

 the theoretical speculations of Mendelejeff, already mentioned. Scan- 

 dium and germanium had not yet been discovered, so that nothing 

 could either justify or confirm the conclusions derived from the law of 

 periodic! t3^ As early as 18G9, in a communication presented to the 

 Eussian Society of Chemistry at St. Petersburg, "on the correlations 

 existing between the properties of elements and their atomic weight," 

 Mendelejeff^ had, in fact, affirmed the existence of simple bodies not 

 yet discovered, whose atomic weight, ought, for example, to be between 

 G5 and 75. He had even gone further yet, by studying and describing in 

 all their details the properties of three hypothetical elements,^ ekabor, 

 eka-aluminum, and ekasilicon. It will be seen, then, what interest 

 attached to the question of ascertaining whether the properties of 

 gallium agreed with the previsions of the Russian chemist. 



At first it seemed that no agreement existed, at least the determina- 

 tion made on the small quantities of gallium that could be obtained 

 gave for its specific gravity the unexpected value of 4.7. But as several 

 of the properties of the new metal, such as precipitation from its solu- 

 tions by carbonate of baryta, its tendency to form basic salts and its 

 capacity for furnishing alums, denoted a very close relationship with 

 aluminum, Mendelejeff' did not hesitate, in the Memoires de I'Academie 

 des Sciences of France, to declare that the element in question seemed 

 to correspond to that whose existence he had foretold in 1871 as analo- 

 gous to aluminum, and which he had provisionally designated under 

 the name of eka-aluminum. And, in fact, new determinations made 

 with more considerable quantities of gallium, obtained by the electro- 

 lytic process, showed that its specific gravity was 59, a value exactly 

 corresponding to that calculated by Mendelejeff' for the hypothetical 

 eka-aluminum. The same agreement was later shown for its specific 

 heat (0.08) as well as for its specific gravity, so that the exactitude of 

 the previsions of Mendelejeff were confirmed. It was thus well estab- 

 lished that it is possible to deduce from the properties of known ele- 

 ments those of elements yet unknown, but whose existence may be 

 predicted. 



Mendelejeff' did not hope for such a rapid confirmation of his pre- 

 visions, but his triumph was still more complete, for to gallium there 

 was soon added scandium (ekabor), discovered by M. L. F. Mlson in 

 1879, and germanium (ekasilicon) by myself in 1886.^ 



' D. Mendelejeff, Journ. d. riiss. chem. Gea., 1869. 

 ^D. MeDdelejeff, Anu. cliem. Siipp., 8. 

 ^Cf. Winkler, Berich. d. d. chem. Gesellsch, 19, 

 SM 97 IG 



