PAPERS OX CHEMISTRY AND PHYSICS 223 



PKEPAEATIOXS OF THE METALS OF THE 

 EAEE EAETH GROUP 



H. C. Kremers, Uxi\ebsity of Iixixois 



The extreme electropositive character of the rare 

 earths renders the preparation of the metals a difficult 

 one. Their isolation is rendered still more difficult by 

 the fact that the separation of the individual members 

 from each other is no mean task. The rare earth ores 

 are fairly abundant, especially those in which the cerium 

 group predominates. In fact, in the incandescent mantle 

 industry thousands of tons of cerium group material are 

 annually thrown away after the extraction of thorium 

 from monazite sand. This enormous waste of rare earth 

 material has been a great stimulus for research on the 

 preparation of the metals. 



There are in general two methods of attack in the iso 

 lation of the metals: Reduction chemically by metals 

 more electropositive in character and electrolysis of fused 

 salts. 



The only metals which have been used more or less suc- 

 cessfully for reduction chemically are sodium and potas- 

 siimi. The method has been paitially successful and that 

 only in the case of the less positive of the rare earths, 

 namely the yttrinm group. The method usually used^ 

 was to mix the anhydrous chloride of the rare earths 

 with the equivalent amount of granulated sodium, plac- 

 ing the mixture in an iron or nickel boat in an iron tube 

 and allo^^ng the reaction to take place tmder a high 

 vacuum. The metal obtained as a fine powder is lixivi- 

 ated with a large amount of water to dissolve away the 

 sodium chloride, undecomposed chlorides and unused 

 sodiimi. The metal powder can then be fused into a co- 

 herent state in a vacuum furnace. This method would, 

 of course, hardly be applicable in a commercial way since 

 it would be far too expensive and slow, but it has been 

 the means of making a study of some of the physical and 

 chemical properties of the rare earth metals. Perhaps 

 the greatest drawback to the method is the fact that the 



1. Hicks. Jour. Am. Chem. Soc ¥>. 1619. 



