SIE WILLIAM CROOKES ON SCANDIUM. 19 



of scandium. A sample of scandia is not considered satisfactory if the least trace 

 of this line is seen on an over-exposed spectrum of scandium, and if the atomic weight 

 is higher than 44'1. The atomic weight of ytterbium being 173, a very little of it as 

 an impurity raises the atomic weight of scandium. 



SCANDIUM HYDROXIDE, 

 Sc 2 3 ,3H 2 = Sc(OH) 3 . 



On adding caustic alkali to a solution of a scandium salt the hydroxide comes 

 down as a bulky gelatinous precipitate. It is insoluble in excess of precipitant. In 

 appearance it resembles yttrium hydroxide. It dries in the air at ordinary tempera- 

 tures to a hard porcelain-like mass and has the composition given above. 



Analysis. 



5 '289 grs. lost on ignition 1'533 grs. of water. 



Theory. Experiment. 



Sc 2 O 3 .... 136-200 7T59 71'02 



3H 2 O 54-048 28 "41 28'98 



190-248 100-00 100-00 



The hydroxide is a very weak base, with a marked tendency to form basic salts. 

 It dissolves readily in dilute acids, forming salts which have a sweet astringent taste. 

 The salts show no absorption spectra. 



After ignition, anhydrous scandia, Sc 2 O 3 , is difficultly soluble in dilute acids in the 

 cold, rather more easily soluble when warmed, and readily soluble in hot strong 

 mineral acids. Strong sulphuric acid poured on ignited scandia attacks it with 

 considerable evolution of heat. ^ 



SCANDIUM CARBONATE, 

 Sc 2 (C0 3 ) 3 ,12H 2 0, 



comes down as a bulky white precipitate on adding ammonium or sodium cai'bonate to 

 a soluble salt of scandium. It is almost insoluble in a cold dilute solution of ammonium 

 carbonate, but is moderately soluble in a hot and strong solution of this salt, and as 

 in the same circumstances yttrium carbonate is much less soluble, this difference 

 may be utilised as a basis for a method of separating scandium and yttrium by 

 fractionation. 



D 2 



