8z3 POPULAR SCIENCE MONTHLY. 



an unknown element which M. K. J. Bayer thought he had 

 found in French bauxite, have returned to nothingness. We men- 

 tion also merely as a matter of curiosity a kosmium and a neokos- 

 mium, deriving their names not from Cosmos, but from Kosmann, 

 who took out a patent for the preparation of their oxides. 



Gallium was discovered in August, 1875, by Lecoq de Boisbau- 

 dran in the blende of Pierrefitte, through two very distinct lines in 

 the violet of the spectrum of that mineral, which, however, as after- 

 ward appeared, contained only a slight proportion of the new metal 

 — not exceeding 0.0001 per cent — while in the richer blende of 

 Bernbryer it amounted to 0.001 per cent. The preparation of gal- 

 lium in any considerable quantities was attended with great difficul- 

 ties on account of the want of a proper mineral to be practicably sub- 

 mitted to the extraction process, and none has as yet been found. 

 Still, the study of the new metal was very interesting, in view of the 

 theoretical speculations of Mendeleef. Scandium and germanium 

 had not yet been discovered, and there was therefore nothing to 

 justify or confirm the conclusions drawn from the law of periodicity. 

 As early as 1869, Mendeleef had affirmed the existence of simple 

 bodies still unknown, the atomic weights of which should be com- 

 prehended between 65 and 75; he had even gone so far as to describe 

 in detail the properties of the three hypothetical elements — eka- 

 boron, eka-aluminum, and ekasilicon. We can imagine the in- 

 terest attached to the question whether the properties of gallium 

 corresponded with the anticipations of the Russian chemist. 



At first, the correspondence did not seem to exist; the deter- 

 minations made on the small quantities of gallium that could 

 be obtained gave the specific gravity the unexpected value of 

 4.7. But as many of the properties of the new metal — such as 

 the precipitation of its solutions by carbonate of barium, its tend- 

 ency to form basic salts, and its capacity of forming alums — 

 denoted a relationship with aluminum, Mendeleef had no hesita- 

 tion in declaring that the new element appeared to correspond with 

 the one the existence of which he had indicated in 1874 as similar 

 to aluminum, and which he had called eka-aluminum. A new de- 

 termination, made with considerable quantities of gallium obtained 

 by electrolysis, brought the value of the specific gravity up to 59, 

 which correspond exactly with the value calculated by Mendeleef 

 for the hypothetical eka-aluminum. The specific heat (0.08) was 

 afterward found to correspond with Mendeleef's estimate, and the 

 justness of his previsions was established. It was therefore shown 

 to be reasonable to deduce from the properties of known elements 

 those of others still unknown, but the existence of which is antici- 

 pated. Mendeleef had not expected so quick a confirmation of his 



