Explain Zone refining.

Explanation

Zone refining :
`rarr`Zone refining is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal.
`rarr` A circular moblie heater is fixed at ome end of a rod of impure metal.
`rarr` The molten zone moves along with the heater moves forward the pue metal crystallises out of the solid state of the melt and the impurities pass into the adjacent molten zone.
`rarr` The above process is repeated severa, times and the heater is moved in the same direction form one end to the other end .At one end impuities get concentrated .This end is cut off.
This method is very useful for producing semicondutor grade metals of very high purity.
Eg : Ge,Si, B, Ga etc....