Metallurgy

Metallurgical Process

Metallurgy is the process of extraction metal from its ore.

Some common metal and ores are –

S. No.	Metal	Ore
1	Aluminum	Bauxite
2	Iron	Hematite
3	Lead	Galena
4	Mercury	Cinnabar
5	Zinc	Calamine
6	Calcium	Dolomite (CaMg(CO3)2)
7	Copper	Chalcopyrite (CuFeS2), Chalcocite (Cu2S)

Natural productions which help us to obtain metal in economic way-
Froth flotation is a process by which hydrophobic substances are added to obtain metal in economic way. Eucalyptus oil is added in to water.

Steps for obtaining metal

1. Concentration
2. Roasting
3. Smelting
4. Reduction
5. Purification

1. Concentration (dressing) of ores

Metallic ores have many impurities like sand or mud this is called gangue or matrix. Ores are concentrated to obtain metal. Some concentration methods to obtain metal –

• Hematite- Lavigation method to obtain metal carbon reduction
• Copper glance to copper.  Froth floatation to reduction
• Bauxite to Aluminum metallic separation to electrolyte reduction
• Cromite ore to chromium magnetic separation to reduction by aluminum
• Silver ore to silver by amalgamation. Amalgamation is process of extracting silver from its ore by using mercury.

2. Roasting

In process of roasting metal, coke or carbon is added in ores and then heated with spontaneous flow of gas.

2Cu₂S + 3O₂ -> 2Cu₂O + 2SO₂
2ZnS + 3O₂ -> 2ZnO + 2SO₂

In this process many harmful products are liberated like arsenic and sulphur dioxide.

Type of roasting metal

• Sinster roasting metal lead sulphides
• Magnetic roasting metal haematite or magnetites
• Chloridising roasting e.g. 2NaCl + Mg + 2O₂ -> Na₂SO₄ + MgCl
• Volatising oxide
• Sulphation

e.g. 2Cu₂S + 3O₂ -> 2Cu₂O + 2SO₂

2ZnS + 3O₂ -> 2ZnO + 2SO₂

Smelting

It is form of extraction of base metal from ores e.g. silver, gold, iron, copper.

Copper smelter are used for smelting ore.

Anodising

When aluminum comes in contact with oxygen it is oxidized To avoid this corrosion a layer of aluminum is coated with oxygen Aluminum is safe Electrolysis of aluminum is done by placing in anode and sulphuric acid Oxygen liberated is coated with aluminum anodising it.

Metallic mixture

Steel – Iron and carbon

German silver – Copper, Nickel, Zinc

Gunmetal – Copper, tin, lead.

Oxidation and reduction

Metals reacts with oxygen present in nature

4Fe+3O₂ -> 2Fe₂O₃

2Ag+O₂ -> AgO

Iron rusts because it is oxidizes in presence of free oxygen. Silver also oxidizes in the same way.

The property of iron and silver is called corrosion to prevent iron from corrosion or rusting we use paint.

Test for rust of iron nail

In first test tube add water and iron nail and close with cork.

In second Test tube add water and iron nail and oil, close with cork.

In third test tube add iron nail and Calcium Chloride.

Result the nail in the first test tube rusts because of present oxygen and humus. In third test tube, calcium chloride (CaCl₂ ) absorbs moisture of atmosphere.