BAXTER AND CHAPIN. — ATOMIC WEIGHT OF NEODYMIUM. 225 



jected. Thus any nitrate less soluble than neodymium nitrate would 

 concentrate in the extreme crystal fraction of the last series. A dia- 

 gram of this treatment follows : 



Series 



103 



110 



Crystal I 1 2 at ions 



JSO 



of Nitrafis fyvn 



t— sA/n AXIOM, crc 



Conce vtrathd 



Nitric Acid. 



PRASeODVMIl/M.trC 



170 «; 



The fractions of the last series, 2923 to 2945, were then converted 

 to oxide by precipitation as oxalate from acid solution and ignition of 

 the oxalate. The different fractions of oxide were all of the same lilac 

 blue color. We could detect no difference in the color of the oxides 

 of fractions found to be essentially free from praseodymium and those 

 containing several tenths of a per cent of this impurity. 



The final fractions were next subjected to careful comparative spec- 

 trographic examination, great pains being taken to have the conditions 

 of experimentation the same for all the fractions. One gram of every 



VOL. XLVI. 



15 



