General Principles and Processes of Isolation of Elements — Chemistry STD 12 Science — Question

Zone refining: The method is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal. A circular mobile heater is fixed at one end of a rod of impure metal. The molten zone moves along with the heater which is moved forward. As the heater moves forward, the pure metal crystallizes out of the metal and the impurities pass on into the adjacent molten zone. The process is repeated several times and the heater is moved in the same direction. At one end impurities get con-centrated. This end is cut off. In this way, the impu-rities are swept from one end of the bar to the other. By repeating the process, ultra pure metal of silicon, germanium etc are obtained.