Refining and purification of rare-earth metals

Abstract

Behavioral differences within the rare earth metal group are sufficiently pronounced to make generalizations in regard to parification of questionable value. In the few cases where the same technique has been applied to two members of the group, the results as often as not have been contradictory. Nevertheless, it would appear that those techniques which are generally most promising for purification of the rare earth metals are distillation and solid state electrolysis. Zone refining may be of value for some impurities, but the van Arkel--de Boer deposition technique appears to hold little promise. None of the techniques with the possible exception of amalgamation is particularly attractive as a production process, and it must be concluded that refinement of the reduction itself is the optimum method for obtaining a pure metal in quantity. A similar conclusion was reached in a recent theoretical survey of metal refining techniques. (auth)