478 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP, 



soluble in ammonium sulphide. The metal forms a 

 soluble trichloride, a soluble sulphate and an alum. 



Ekasilicon. Germanium. 1 



Atomic Weight 5 = 72 Ge=72'5 



Density Es, 5-5 Ge, 5-469 



Density of Oxide EsO 2 , 4*7 GeO 2 , 4'73 



Density of Chloride EsCl 4 , 1-9 GeCl 4 , 1-887 



B.P. of Chloride <ico 86C. 



Density of Ethide Es(C 2 H 5 ) 4 , 0-96 Ge(C 2 H 5 ) 4 , <i 



B.P. of Ethide 160 160 



The metal, prepared by reducing the oxide, or by 

 the action of sodium on the double fluoride, is not 

 easily fusible, but burns to a very refractory white 

 dioxide. The oxide is feebly basic ; on adding acid to 

 its alkaline solutions, it may remain in solution as a 

 soluble hydrate or be precipitated as an insoluble 

 metahydrate. The disulphide is insoluble in water, but 

 dissolves in ammonium sulphide. The fluoride, like the 

 chloride, is a volatile liquid. 



In the range covered by the rare-earth elements Men- 

 dele'efFs predictions were less successful, thus Ekacaesium, 

 EC =175, and Ekaniobium, 11=146, are still unknown; 

 but Mendele'eff was struck by " the absence ... of almost 

 a whole long period (beginning from Ce=i4o)" and 

 concluded that this " can scarcely be regarded as accidental 

 and probably has its origin in the nature of the elements " 

 (Ann. Chem. Pharm.^ 1872, 8, Suppl., 205). On the other 

 hand his Ekamanganese, Em = 100, and Trimanganese, 

 Tm = 190, are still to be looked for, whilst his Dwicsesium, 

 Dc=22o, and Ekatantalum, 1 = 235, correspond with two 

 of the three gaps at the commencement of the radioactive 

 Period VII. 



Secondary relationships in the periodic system. The 

 classification of the elements by vertical columns into 

 groups and families has come to be regarded as the 



1 For a more detailed comparison, see Freund, Study of Chemical 

 Composition, pp. 480-481. 



