(a) Give two points of differences between pig iron and cast iron.
(b) Outline the principle of zone refining.
(a) Pig iron :
(1) It is iron obtained from blast furnance.
(2) It contains 4% carbon and small amounts of S, P, Si and Mn and is impure.
Cast iron :
(1) It is obtained by melting pig iron with iron scrap.
(2) It contains 3% carbon.
(b) Zone refining is based on the principle that the impurities are more soluble in molten state than in solid state of metal.