

SIR WILLIAM CROOKES ON SCANDIUM. 27 



My own analytical results agree closely with NILSON'S formula. As CLEVE distinctly 

 says that the double sulphate is soluble in a saturated solution of potassium sulphate, 

 it is probable he was not working on the true double salt. 



The scandia in the aqueous washings was also determined. The total amount of 

 scaiidia in the washings and precipitate amounted to 4'560 grs., which, added to the 

 0'414 in the solution, makes 4 '974 grs. of scandia. The 17717 grs. of scandium 

 sulphate contain theoretically 4 - 981 grs. of scandia, so these results are well within 

 experimental errors. 



SCANDIUM SELENATE, 

 Sc 2 (Se0 4 ) 3) 8H 2 0. 



Dilute and warm selenic acid easily dissolves scandium hydrate or carbonate, and 

 on evaporating the acid solution over sulphuric acid the selenate crystallises in well- 

 defined rhombic prisms, bright, colourless, and capable of withstanding a temperature 

 of 400 without decomposition, except loss of water. 



When heated to 100 for sixteen hours, the 8-hydrate loses 6 molecules of water 



and becomes a 2-hydrate, 



Sc 8 (Se0 4 ) 3 ,2H 8 O. 



Analysis. 



(1) 16 '847 grs. of crystallised scandium selenate, heated to 400, lost 3709 grs. of 



water. 



(2) 16'847 grs. of the same salt gave on ignition to a full yellow heat 3'485 grs. of 



scandia, = 2'257 grs. of scandium. 



(3) 13'913 grs. of the crystallised salt, heated to 100 for sixteen hours, lost 



2 '2 9 3 grs. of water. 



Theory. Experiment. 



661-928 100-00 lOO'OO 



The anhydrous selenate, heated to a full yellow heat, loses all the selenic acid, and 



scandia remains. 



Analysis. 



13-138 grs. of anhydrous seleiiate left 3'485 grs. of scandia, = 2'257 grs. of 

 scandium. 



E 2 



