THE CLASSIFICATION OF THE ELEMENTS 477 



These were vindicated in a striking way by the discovery of 

 ;he three patriotically-named elements 



scandium, gallium, germanium, 



(Nilson, 1879) (Boisbaudran, 1875) (Winkler, 1886) 



Some of the chief predictions, and their verification, are set 

 out below. In the case of scandium or ekaboron, the pro- 

 perties of the metal and its anhydrous chloride were pre- 

 dicted by Mendeleeff, but are still unknown. The narrative 

 shows the most important points of agreement between 

 MendeleefFs predictions and the observed properties of the 

 three elements. 



Ekaborop. Scandium. 



Atomic Weight Eb = 44 Sc = 44- 1 



Formula of Oxide Eb 2 O 3 Sc 2 O 3 



Density of Oxide 3*5 3'8 



The oxide is a weak base, intermediate between 

 alumina and magnesia. It forms a gelatinous hydrate, 

 carbonate and phosphate. The sulphate is soluble (but 

 less so than aluminium sulphate). The chloride is more 

 easily hydrolysed than MgCl 2 , liberating HC1. The salts 

 are colourless. 



Ekaaluminium. Gallium. 



Atomic Weight 68 69-9 



Density 5-9 5-93 



Melting-point { ^^ } 3'iC. 



Formula of Oxide Ea 2 O 8 Ga 2 O 3 



Density of Oxide 5*5 



The metal is not volatile ; it is attacked slowly by air 

 and water, by acids and by alkalis. The oxide being 

 more basic than A1 2 O 3 and less basic than MgO, it is 

 precipitated by barium carbonate. The gelatinous 

 hydroxide is soluble in acids and alkalis. The sulphide 

 is precipitated by sulphuretted hydrogen and is not 



