24 SIR WILLIAM CROOKES ON SCANDIUM. 



and the rest at a higher temperature." He found on analysis 14'26, 14'46, and 7'16, 

 7'29 of H 2 0, instead of 14'88 and 7'44. 



I have crystallised this sulphate from a syrupy aqueous solution ; it is dried by 

 repeated pressure between many folds of blotting-paper. 



Analysis. 



(1) 18'15G grs. of the crystallised G-hydrate, finely powdered, and heated to 100 



for three hours, lost 2 '602 grs. of water, leaving a 2-hydrated sulphate. 



(2) 20725 grs., kept in a desiccator over sulphuric acid for 170 hours, lost 1'561 



grs. of water, leaving a 4-hydrated sulphate. 



(3) 29'138 grs. left on ignition 8'068 grs. ofscandia. 



(4) 31 '508 grs. of the liquid sulphate, precipitated from solution on adding alcohol 



containing a little ether, were dissolved in water, and the scandia precipitated 

 by ammonia. When dried and ignited it weighed 8 '624 grs. 



Theory. Experiment. 



(1), (2), (3), and (4). 

 Sc 2 3 .... 136-200 28-11 27-53 



3SO 3 240-180 49-58 50'61 



2H 3 .... 36-032 7-44 7 "53 



4H 2 . . . 72-064 14-87 14-33 



484-476 100-00 lOO'OO 



The 6-hydrate effloresces in a dry atmosphere, and loses one molecule of water, 

 becoming the 5 -hydrate, which appears to be the most stable hydrate at ordinary 

 temperatures : 



Sc 2 (S0 4 ) 3 ,5H 2 0. 



Analysis. 



(1) 16'619 grs. of the 5-hydrate, heated to 150, lost 3'206 grs. of water. 



(2) 16-619 grs., after drying as described and igniting to a yellow heat, left 



4 - 8 7 8 grs. ofscandia. 



(3) 15-608 grs. of the 5-hydrate, heated in vacua at 100 for twenty hours, and 



then for ninety minutes at 150, lost 3 '15 3 grs. of water. Ignited to a full 

 yellow heat, it left 4 '5 5 8 grs. ofscandia. 



(4) 38-819 grs., heated to just below visible redness, lost 8'019 grs. of water. 



(At this temperature a trace of basic sulphate is formed. This accounts 

 for the excess over the theoretical loss of water.) 



