i62 POPULAR SCIENCE MONTHLY. 



silicon, in several cases going into considerable detail as to the proper- 

 ties of the elements and their compounds. It was in 1875 that the 

 first of these predictions was fulfilled in the discovery of gallium by 

 Lecoq de Boisbaudran. This metal fell in the place which Mendeleeff 

 had given to eka-aluminum, and its specific gravity is 5.9, while 5.8 was 

 the figure which had been foretold. Four years later Nilson discovered 

 eka-boron, and gave to it the name scandium. In 1885 a new silver 

 mineral, argyrodite, was found in the Freiberg mines, and every an- 

 alysis made of it showed a discrepancy of six or seven per cent. This 

 soon led to the recognition by the analyst, Clemens Winkler, of the 

 presence of a new element, and it further appeared that this new ele- 

 ment was Mendeleeff's eka-silicon. Not to be outdone by the French 

 and Swedish chemists, Winkler patriotically called the new metal ger- 

 manium. It is worth while to show side by side, a few of the predic- 

 tions of the properties of eka-silicon, published by Mendeleeff in 1872, 

 and the actual properties of germanium, as experimentally determined 

 by Winkler in 1886: 



Eka-Silicon. Symbol, Es. Germanium. Symbol, Ge. 



ELEMENT. 



Atomic weight, 72. Atomic weight, 72.3. 



Specific gravity, 5.5. Specific gravity, 5.469 at 20'. 



OXID. 



Formula, EsOz. Formula, GeOj- 



Specific gravity, 4.7. Specific gravity, 4. 703 at 18°. 



CHLOBID. 



Formula, ESCI4. Formula, GeCl^. 



Liquid, boiling a little below 100°. Liquid, boiling at 86°. 



Specific gravity, 1.9 at 0°. Specific gravity, 1.887 at 18°. 



MKTALLO-ORGANIC COMPOUND. 



Formula, Es (C2Hb)4. Formula, Ge (CisHb)4. 



Liquid, boiling point, 160°. Liquid, boiling point, 160°. 



Specific gravity, 0.96. Specific gravity, slightly leas than 



water (which is 1.0). 



So close is this agreement that it is difficult to realize that Men- 

 deleeff's forecasts were put in print more than a decade before the 

 element had ever been handled by man. 



Since the corrected form of Mendeleeff's table was published in 

 1871, there has been no end to the speculation upon the subject, and 

 dozens of tables, emphasizing different relations of the elements, have 

 been proposed. Few of these have equaled that of tlic Russian chemist 

 in simplicity or have as few obscure points. One of these tables, sug- 

 gested a few years ago by Dr. F. P. Venable, of the University of North 

 Carolina, may be noticed as presenting some decided advantages over 

 that of Mendeleeff: 



