Zinc occurs naturally as sulfide and carbonate ores. It is extracted through crushing, concentration, roasting, and reduction processes. The concentrated ore is roasted in air to convert zinc sulfide to zinc oxide. The zinc oxide is then mixed with coke and heated in a vertical retort furnace to produce zinc vapors, which condense to produce molten zinc. The molten zinc is further purified through electrolysis to produce high purity zinc. Zinc is a bluish-white metal with a melting point of 420°C. It is used for galvanization of iron and in making alloys like brass and German silver.

1. Zinc (Zn)
Group IIB At. No=30 At. Wt=63.5
Configuration : [Ar]3d10 4s2
Occurrence:
Zinc occurs in nature only in combined state. The main ores of zinc are:
Zinc blende – ZnS Calamine – ZnCO3
Zincite – ZnO Franklinite – ZnO. Fe2O3
Willimite – 2ZnO. SiO2
Extraction of Zinc from Zinc Blende
Crushing and Concentration:
The ore is crushed in jaw crushers and then powdered finely. Zinc blende being sulphide is
concentrated by froth floatation method. The powdered ore is kept in water containing pine oil &
the mixture is agitated by passing compressed air. Ore forms froth with oil and come to the
surface and are skimmed off while impurities are left in water
Roasting:
The concentrated are is heated in excess supply of air about 9000c in the hearth of reverberatory
furnace. During roasting zinc sulphide is converted to Zinc Oxide.
2ZnS + 3O2 → 2ZnO + 2SO2
Small amount of ZnS may be oxidized to ZnSO4 but above 9000c , ZnSO4 decompose forming
Zinc Oxide (ZnO)
ZnS + 2O2 → ZnSO4
ZnSO4
above 900 → 2ZnO + 2SO2 + O2
Reduction (Smelting):-
ZnO obtained during roasting is mixed with coke and heated strongly where ZnO is reduced to
Zn by carbon.
ZnO + C → Zn(vapours) + CO
Figure: Vertical retort furnance for the extraction of zinc

2. The reduction is done in vertical retort. In this process roasted are mixed with coke
in the ratio of 2:1 and small briquets are made. These briquets are fed into vertical
retort furnance, from the charging door. The report is heated externally by burning
producegas (CO+N2) to about 14000c. The vapour of Zn and CO so produced are
allowed to pass to the condenser by applying a suction and passing a current of
producergas from the bottom as shown in figure. In the condenser, vapours of zinc
get liquefied and molten zinc is obtained as spelter and CO escapes out through the
outlet. The molten Zn, the spelter is taken out from the condenser from time to
time and residues are taken out from the bottom of the retort.
Purification:-
Zinc spelter contains Pb, Fe, Cd, As, etc. as impurities. Impure zinc can be purified
by
a. Electrolysis:-
Zinc of higher purity can be obtained by electrolysis. Pure zinc rod is used as
cathode while a block of impure zinc is used as anode. A mixture of ZnSO4 and dil
H2SO4 is used as electrolyte. On passing current impure zinc dissolves and
equivalent amount of pure zinc is deposited at cathode.
At cathode: Zn++(aq) +2 e- → Zn
At anode: Zn → Zn++ (aq) +2e-
PhysicalProperties
i. It is a bluish white lustrous metal.
ii. Zinc is brittle at ordinary temperature but it becomes malleable from 100-150o c
then again it becomes brittle.
iii. It melts at 420oc and boils at 900o c and has sp. Gravity 7.13.
Uses of zinc:
- It is used for galvanization of iron.
- It is used in making alloys like Brass (Cu+Zn), German silver(Cu+Zn+Ni), etc
-its compound are used in medicine and paints.
-it is used as cathodein dry cell
Vertical retort: A flask with a rounded base and a long neck that is bent down and tapered,