The impure zinc contains impurities such as cadmium, arsenic, iron and lead. From this, zinc may be recovered by

Impure zinc contains impurities of cadmium (b.p.1073 K) lead (b.p.2024 K) and iron (b.p.3273 K). The boiling point of zinc is 1180 K. The impure metals is distilled when zinc and cadmium with low boiling points dist over leaving behind lead and iron. The boiling points of Zn and Cd differ by about 100 K, therefore, the mixture of Zn and Cd is again subjected to fractional distillation when low boiling Cd distils over leaving behind zinc metals in the distillation flack.