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Tin is a silvery, malleable metallic element and it belongs to the group IV of the periodic table. it is characterised by the folowing.

1. Atomic number 50
2. Relative atomic mass 118.690
3. Relative density 7.291
4. Melting point 231.97^OC
5. Boiling point 2270^OC
6. Is highly malleable and ductile.

The tin-stone is crushed and finely powdered in ball mills. The crushed ore can be concentrated by the following method.

Wilfrey table method

In this method the crushed ore is fed on to the top of a special rolling table. This table consists of a slanting floor on which long wooden strips called cleats or riffles are fixed. A running steam of water is made to flow across the table at right angles to the slope. The table is kept vibrating al the time. As a result of all this, the lighter silicous and earthy gangue particles rise up and are carried away with water while the heavier ore particles settle at the bottom.

The magnetic particles are then separated by the magnetic separation method. By this method an impurity, wolframite, which is magnetic is separated.

2. ROASTING

in this process the concentrated ore is heated strongly in an inclined revolving furnace in a free supply of air. The following reactions take place.

S+O_2è SO₂

4As + 3O₂ è 2As₂O₃

4Sb + 3O₂ è 2Sb₂O₃

CuS + 2O₂ è CuSO₄

FeS + 2O₂ è FeSO₄

The roasted ore is now cooled and extracted with dilute sulphuric acid when CuSO₄ and FeSO₄ formed dissolve in it and are thus washed away. The ore obtained at this stage contains about 75% of SnO₂ and is called black tin.

3. SMELTING

The black tin obtained above is mixed with anthracite coal and heated in a reverbatory furnace at 1200^OC - 1300^OC. if silica is present as an impurity, a little lime or fluorspar is added as a flux. The following reaction occurs in the furnace.

SnO₂ + 2C è Sn + 2CO

The tin obtained above is 70% pure and is called block tin.

The impure metal is then purified.