This is a simple pdfh to understand Metallurgy in a more convinient way.

1. General Principles of Metallurgy
• A few elements like carbon, silver, gold and noble gases occur in free state,
while others are present in combined state in earth’s crust.
• Most of the metals occur as their minerals.
• For obtaining a particular metal, first we look for minerals; they are naturally
occurring chemical substances in the earth’s crust obtained by mining.
• The branch of science deals with different methods of extracting the metal
from its natural sources and then converting them into useful materials to
the mankind is known as metallurgy.
• The minerals which are suitable for extraction of metal by applying simple
methods and gives high percentage of metal are called ORES.

2. A. Occurrence:
• Metals occur mostly as their oxides, carbonates, sulphides, chlorides.
• The ores of aluminum, iron, copper and zinc have been given in the table
below.

3. B. Principle of Extraction: (Extraction of metals)
• The minerals available in nature contain various types of impurities.
• Some impurities are combined with the minerals either physically or chemically.
• So depending on the nature of the impurities, different types of treatment of
the ore are adopted. Some of these treatments are described here.
a) Ore Concentration:
• Removing of the unwanted materials (e.g., sand clay, stones etc.,) from the ore
is known as concentration (or) dressing (or) benefaction.
• The impurities of certain types can be eliminated from the ore in the molten
state only.
• Most of the impurities in the ores do not melt easily at the temperature of the
normal industrial furnaces. Therefore “ an outside substance, added to the ore
to lower its melting point, is know as flux.”
• “Flux combine with the gangue (i.e., impurities of the ore) chemically and
forms easily fusible products, called slag”.
• “since this entire process is costly, the gangue is removed first by other cheap
physical methods. Some of the common methods of ore dressing are
described here.

4. Crushing of Ore: Generally metals occur in the form of larger lumps these lumps
are crushed into small particles by using jaw crushers and grinders.
i) Hand picking:
• When ore particles and gangue particles are having different physical
appearances then this method is used. Selected pieces of ores are picked by
hand.
ii) Hydrolytic washing:
• The crushed ore is washed in a stream of water. The lighter impunities are
swept away while heavier particles settle down.
• This is based on the differences in gravities of the ore and the gangue
particles. It is also called gravity separation.
• Iron ores and tin ores are concentrated by this method.

5. iii) Magnetic Separation:
• The process is meant for the separation of magnetic ore from impurities.
• In this method the powdered ore is placed over a leather belt which
moves over two rollers one of which is magnetic.
• When the crushed ore is passed over magnetic roller, magnetic ore
particles are attracted by it and fall nearer to it while impurities fall away
from the magnetic roller.
• Chromite [Fe(CrO2)] from siliceous gangue, rutile (TiO2) from cholrapatite
and wolframite (FeWO4) from casiterite are separated by this method.

6. iv) Froth Floatation method:
• This method has been in use for removing gangue from sulphide ores.
• In this process, a suspension of the powdered ore is made with water. To
it, collectors and froth stabilizers are added.
• Collectors (ex: pine oil, fatty acids, xanthates etc.,) enhances non-wet
ability of the mineral particles.
• Froth stabilizers ( ex: cresols, aniline) stabilize the froth.
•The mineral particles become wet by oils
while the gangue particles by water.
•A rotating paddle agitates the mixture and
draws air in it. As a result, froth is formed
which carries the mineral particles.
•After attachment of all ore particles to foam,
this is shifted or collecting in another tank,
then ore particles settled down at the bottom
and foam is evaporated.

7. 5. Liquefaction:
• This method is useful for such ores which contain fusible mineral particles
and high melting gangue.
• This method is used with stibnite and antimony mineral.
• It is taken in a fire clay pots with perforated bottom and heated to around
500-6000 c. Only the mineral part of the ore melts and flows out leaving
the gangue behind.

8. b. Oxidation:
• The most commonly used oxidizing agent in the metallurgy is O2 .
C. Reduction:

9. e) Metals like Al, Mg or Ca are also used for the reduction. When Al is used as a reducing agent,
the process is referred as Goldschmidth’s Alumino Thermic process.
These reactions require high
temperature and here the metal is
obtained in molten state.

10. d) Electrolytic method- refining:
• Zn,Cu,Ag,Au etc., impure metals are refined by this method.
• In this method, the impure metal is anode and the pure metal is cathode. An
acidified solution of the metal salt is electrolyte.
• On passing electricity pure metal is deposited on the cathode. The impurities
settle to the bottom at the anode. This is know as anode mud.

12. B. Extraction of copper from sulphide ore:
• Copper pyrites is the main source of copper metal. From it copper metal is
obtained by the following process.
a) Concentration:
• The finely crushed ore is concentrated by Froth-Flotation process.
• The finely crushed ore is suspended in water containing a little amount of
pine oil.
• A blast of air is passed through the suspension. The particles get wetted by
the oil and float as a froth. The gangue sinks to the bottom.
• The froth is separated and about 95 % concentrated ore is obtained.

13. b) Roasting:
• The concentrated ore is then roasted in a furnace in presence of air.
• Sulphur is oxidized to SO2 and impurities of arsenic and antimony are
removed as volatile oxides.

14. C) Smelting:
• The roasted ore is mixed with coke and silica (SiO2) and is introduced into a
blast furnace. The hot air blast converts FeO into ferrous silicate (FeSiO3).
• The product of the blast furnace consists mostly of Cu2S and a little of ferrous
sulphide. This product is known as “Matte”. It is collected from the outlet at the
bottom of the furnace.

15. d) Bessemerization process:
• Copper metal is extracted from molten matte through bessemerization.
• The matte is introduced in to Bessemer converter through tuyers.
• The air is blown through the molten matte.
• Blast of air converts Cu2S partly into Cu2O which reacts with remaining
Cu2S to give molten copper.
• The copper so obtained is called “Blister copper” (98 % pure).

16. e) Refining of copper:
• Blister copper is refined by electrolysis.
• Blocks of blister copper (impure copper) are used as anodes and thin
sheets of pure copper act cathodes.
• The cathode plates are coated with graphite in order to remove deposited
copper. The electrolyte CuSO4 mixed with a little amount of H2SO4 to
increase the electrical conductivity.
• During electrolysis, pure copper is deposited on the cathode plates and
impurities which are soluble and fall to the bottom of the cell as anode
mud.
Uses: It is used as thermal conductor, an electrical conductor, a building
material and a constitute of various metal alloys.
• This eclectically refined copper is 100 % pure.

17. Zinc
Occurrence:
• Zinc is a metallic chemical element with the symbol Zn and atomic number
30.
• Zn is the 24th most abundant element in the earths crust and has five
stable isotopes.
• Zn deficiency affects about 2 billion people in the developing world and is
associated with many diseases.
• Zinc is not found in the native state. Its important minerals are given in the
table below.

18. Extraction of zinc from sulphide ore:
• The metal Zn can be extracted from its minerals in different ways depending
on the ore.
• Zinc pyrites is main source of zinc metal.
• Following steps are involved in extraction of zinc.
a) Concentration:
• The finely crushed ore is concentrated first by gravity separation process.
• The crushed ore is washed with a stream of water on a wilfleys table, The
table.
• Due to the motion the lighter gangue particles are washed by the steam,the
heavier particles settle to the bottom of the table.
• They partly concentrated ore is futher concentrated by froth floataion
process. The ore particles go with the froth.
If iron oxide is present in the gangue, the
concentrated ore is subjected further to
electromagnetic separation iron oxide is
magnetic and so forms a heap nearer to the
magnetic pole.

19. b) Roasting:
• The concentrated ore is then roasted in a furnace in the presence of air. Sulphur
is oxidized to SO2 and impurities of arsenic and antimony are removed as
volatile oxides. The following reaction takes place.
• If calamine is the starting material for extraction the ore is directly calcined to
get zinc oxide.

20. c) Reduction:

21. d) Refining of Zinc:
• Electrolysis is performed in lead-lined concrete cells.
• Anodes are made of lead containing 0.5-1.0 % silver and cathodes are made
of aluminium sheet.
• The electrolyte is Zinc sulphate solution containing a little H2SO4.
• The Zinc deposited is deposited on cathode.
• The purification of the electrolyte ensures that normal product will reach
purity of 99.99 %

22. Occurrence and principles of
extraction of Fe
A) Occurrence:
• Iron is the second most abundant metal after Al and fourth most abundant
element in the earth’s crust.
• It is mostly occurs in the combined state.

23. B) Principles of extraction of Fe:
The chemistry of iron can be studied under three sections depending upon the
type of iron required. The sections are
a) Manufacture of cast iron (Fe + 4% C)
b) Manufacture of wrought iron ( Fe + 0.2 % C)
c) Manufacture of steel ( Fe + 0.5-1.5% C)
a) Manufacture of cast iron:
• Iron is extracted from its from its oxides in a blast furnace. This is an almost
cylindrical furnace, lined inside with fire bricks.
• It is charged from the top with an iron ore (8 parts), desulphurised coke (4
parts) and lime stone (1 part) and is mixed in 8:4:1 parts by weight.
• Air is blown from the bottom. The coke burns producing heat and CO.
• The temperature range in the furnace is 3000 - 16000 c.
• Various reaction take place in the blast furnace at different temperature and
different zones.

25. • The iron obtained is known as Pig iron.
• The solid iron obtained by cooling pig iron is called as cast iron. It contains
nearly 4% C.

26. b) Manufacture of wrought iron:
• Wrought iron is the purest form of iron containing about 0.2 % C.
• It is prepared by heating cast iron in a reverboratory furnace.
• The furnace is given a basic lining of iron oxide.
• The impurities and the carbon present in cast iron combine with the lining. The
impurities form a slag and carbon is oxidized to CO and escapes.
• It burns with a blue flame. The flames are known as “puddlers cnadles”. Hence
the process is known as Puddling process.
Carbon and various impurities present
combine with lining and form slag.

27. C) Manufacture of steel:
• Steel contains ( Fe + 0.5-1.5% C).
• It is prepared by blowing air through molten pig iron taken in Bessemer
converter.
Bessemer converter process:
• The Bessemer converter is a pear shaped furnace.
• It is constructed with steel.
• It is lined with silica or lime depending on the proportions of impurities present
in the iron (P, Si, Mn and C).
• Air is forced through the inlets at the bottom.

28. • Carbon and various other impurities present combine with oxygen and form
slag.

29. Process of molten electrolysis of Al &
Mg

30. Aluminium
a) Occurance:
• In earths crust, aluminium is the most abundant (8.3 % by weight)
metallic element and third most abundant of all elements ( after oxygen
and silicon).
• It is never found in the elemental state.
• The importance minerals of Al are given below.

31. b) Extraction:
• For the purpose of extraction of Al, bauxite is by far the important source.
• From bauxite Al is obtained by electrolysis.
• For this purpose pure bauxite is necessary.
• The following steps are used in extraction of aluminium.
i. Purification of Bauxite
ii. Electrolytic reduction of alumina
iii. Refining of aluminium

32. i. Purification of Bauxite:
• Bauxite containing iron oxide as impurity is known as red bauxite.It is purified
either by Baeyers process or by Halls process.
• where as bauxite containing silica as impurity is known as white bauxite and is
purified by serpeks process.

35. :

36. ii. Electrolytic reduction of Alumina:
• In the metallurgy of aluminium, purified Al2 O3 obtained from bauxite is mixed with
Na3AlF6 which lowers the melting point of the mixture and makes it conductivity.
• Electrolysis is carried out in and iron or steel tank. The tank is lined inside with the graphite that
acts as cathode. Anode consists of a number of carbon rods. Suspended from the top of the
electrolytic cell.
• The anodes are immersed partially into the electrolyte. The electrolyte consists of a fused mixture
of alumina, cryolite. The surface of the electrolyte is covers with powdered coke. This prevents the
oxidation of the metal formed in electrolysis.
• The following reaction takes place in the electrolytic cell.

37. • Aluminium ions move towards the cathode (i.e. carbon lining) and they are
discharged. Aluminium metal is formed. Fluoride ions are discharged to give
fluorine at the anode.
• Aluminium produced at the cathode, sinks to the bottom to the bottom of the
cell. It is removed from time to time through tapping hole. Fluorine formed at the
anode reacts with alumina. Alumina is added at intervals. In this process, 99%
pure aluminium is obtained.

38. iii. Refining of Aluminium:
• Aluminium obtained by the above process contains impurities like Si, Cu, etc. It
is further purified by Hoope’s electrolytic method.
• The electrolytic cell used for refining of aluminium consists of an iron tank lined
inside with carbon. It contains three layers of fused masses. These layers differ
in their specific gravities.
• The upper layer is of pure aluminium.
• A number of graphite rods acts as cathode. They are suspended from the top
into the upper layer.
• The middle layer consists of a fused mixture of fluorides of sodium, barium and
aluminium. This layer acts us an electrolyte.
• The bottom layer contains impure aluminium.

39. • On passing current Aluminium ions from the middle layer, are discharged at
the cathode layer (upper layer), pure Al is deposited in the upper layer.
• At the same time an equivalent amount of aluminium passes into the middle
layer from the bottom layer.
• 99.89 % Al is the result of this process.

40. Magnesium
a) Occurrence:
• Magnesium being quite reactive does not occur in the free state in
nature but it will occur in the combined state.
• It is present in sea water as halides, in animal blood, in vegetable
kingdom as chlorophyll.

41. Electrolysis of fused magnesium chloride:
• Fused MgCl2 is obtained from carnalite (KCl.MgCl2.6H20)
• { Molten mixture of MgCl2 and NaCl } – Electrolyte.
NaCl decreases the melting point of the mixture and increases the electrical
conductivity of MgCl2 .
• The molten mixture of MgCl2 and NaCl is electrolyzed in an iron cell through which an
inert gas or coal gas flows to avoid any reaction between the liberated metal and
oxygen/ nitrogen of the air.
• The cell wall acts as the cathode. While the carbon rod dipping into the metal acts as
anode. Magnesium is obtained at the cathode and chlorine is evolved at anode. The
reaction takes place as follows.
The liberated metal being lighter than
the electrolyte floats over the surface.
Chlorine evolved at anode as a by-
product. Metal of 99.9 %. Pure Mg is
obtained by this method.

42. Electrolysis of fused magnesium oxide:
• Magnesium metal can also be obtained from Magnesite (MgCO3).
• Magnesia mixed with (Mg, Ba & Na ) flourides - Molten mixture. (
electrolyte)
• Electrolysed the molten mixture in steel tanks at 900-9500C.
• Iron rods – Cathods
Carbon rods – anodese
Electrolyte – Molten mixture
• Electrolysis -