224 ILLINOIS STATE ACADEMY OF SCIENCE 



reaction of sodium and a rare earth chloride is a reversi- 

 ble one, and that metallic sodium can very easily be pre- 

 pared by the interaction of a rare earth metal and sodium 

 chloride. 



Electrolysis of the fused salts of the rare earths has 

 been in commercial use for several years. This has, of 

 course, only been applied to the production of cerium 

 group metal or "misch metal". Several tons of misch 

 metal have been made annually in this country alone dur- 

 ing the late war. Considerable use of this metal was 

 made in igniters for hand grenades, tracer bullets and 

 trench lighters. The raw material in the production of 

 misch metal has always been the double sodium cerium 

 group sulfates obtained as a by-product in the incandes- 

 cent mantle processes. The waste liquors after the ex- 

 traction of Thorium are simply acidified with sulfuric 

 acid, and upon the addition of NaCl the double sodium 

 cerium group sulfates will precipitate out. The double 

 sulfates are then converted to the rare earth hydroxides 

 by treatment with strong hot sodium hydroxide solution 

 and the soluble sodium salts filtered off. The hydroxides 

 are then converted to neutral chlorides, filtered to re- 

 move any rare earth phosphates that may have formed 

 and dehydrated. The anhydrous chlorides are electrol- 

 ized, using a cast iron pot as cathode and a graphite rod 

 as anode. The melting point of the bath is usually suffi- 

 ciently high to melt the misch metal as fast as it is 

 formed. The melting point of misch metal is about 

 750° C, well below that of the melting point of the anhyd- 

 rous chloride, the latter being about 950° C. It is thus 

 evident that in the electrolysis of the fused chlorides of 

 the cerium group or in general any of its members, the 

 melting point of the metal being below or near that of 

 its anhydrous chloride, the metal is easily obtained in a 

 coherent state. Excessively high temperatures of the 

 bath are not necessary and there is very little volatiliza- 

 tion of the latter. Considerable interest has been shown 

 in the use of misch metal as a deoxidizer for cast iron,^ 

 steel and other alloys requiring a scavenger to clean the 



1. Maldenke. Iron Age 105, 324 (1920). 



