46 Browning and Roberts — Separation of Cerium. 



faint didymium bands. In experiment (6) the indication of 

 the presence of didyminm was very faint. In another experi- 

 ment the same amount of material used in (5) and (6), 10 grams, 

 was subjected to a fourth and fifth treatment with bromine, 

 the fourth treatment yielding a small fraction of a gram of the 

 oxides, and the fifth only a few milligrams. In both cases 

 these oxides were free from cerium. The oxides from the first 

 filtrates were much lighter in color than those obtained from 

 the last, which, of course, indicates that the lanthanum is 

 dissolved by the action of the bromine more readily than the 

 didymium. The results follow in the table : 



Mixed oxides Oxides found Oxides found Oxides found 



Total 





taken 



in first 



in second 



in third 



oxides 







nitrate 



filtrate 



filtrate 



found 





grm. 



grm. 



grm. 



grm. 



grm. 



(1) 



1-0000 



0-3310 



0*0720 



0-0190 



0-4420 



(2) 



1-0000 



0-2900 



o-ioio 



0-0420 



6-4330 



(3) 



1-0000 



0-2250 



0-1290 



0-0640 



0-4180 



(4) 



1-0000 



0-2750 



0-0860 



0-0740 



0-4350 



(5) 



10-0000 



3-1360 



1-0050 



0-5930 



4-7340 



(6) 



10-0000 



3-4590 



0-5240 



0-8560 



4-8390 



So it has been shown that by substituting bromine for chlo- 

 rine in the Mosander process about 50 per cent of the other 

 cerium earths can be separated from eerie hydroxide in one 

 treatment, and that after three treatments practically all the 

 other cerium earths are removed without any solvent action 

 upon the eerie hydroxide. The advantages of the method are, 

 the convenience in the use of the bromine, and the apparent 

 lack of tendency of the hydrobromic acid to dissolve the 

 eerie hydroxide. 



An experiment was made, using iodine in place of bromine, 

 as follows : The precipitated and suspended hydroxides from 2 

 grams of the mixed oxides were treated with 1 gram of solid 

 iodine. After standing for about two hours on a steam bath, 

 the excess of iodine was removed by boiling, and the residue of 

 hydroxides was filtered off. The filtrate gave 0-0980 grm. of 

 oxides, free from cerium, and of a slight brown color. This 

 shows that the action of iodine is the same, in a general way, 

 as that of chlorine and bromine, but is too incomplete to be of 

 any practical value. 



