W. O. BAKER 



Figure i. (a) Zone refining technique, discovered by W. G. 

 Pfann, who is adjusting apparatus. By melting a little cross- 

 sectional volume of a rod, or even hollow cylinder, and moving 

 the molten "zone" along the length, manv substances are ex- 

 quisitely purified and, also, made into highly perfect, large single 

 crystals, (k) Single crystals of elements purified by zone melting. 

 From top of figure downward: molybdenum, silicon, germanium, 

 aluminum, silver, and zinc. 



dislocations was finished just before nearly perfect, pure crystals 

 of germanium, prepared by zone refining, revealed crystal 

 dislocations, at last. 



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