Tin

Tin: the essentials

 Brief description: ordinary tin is a silvery-white metal, is malleable, somewhat ductile, and has a highly crystalline structure. Due to the breaking of these crystals, a "tin cry" is heard when a bar is bent. The element has two allotropic forms. On warming, grey, or α-tin, with a cubic structure, changes at 13.2°C into white, or β-tin, the ordinary form of the metal. White tin has a tetragonal structure. When tin is cooled below 13.2°C, it changes slowly from white to grey. This change is affected by impurities such as aluminium and zinc, and can be prevented by small additions of antimony or bismuth. The conversion was first noted as growths on organ pipes in European cathedrals, where it was thought to be the devils work. This conversion was also speculated to be caused microorganisms and was called "tin plague" or "tin disease".

Tin resists distilled, sea, and soft tap water, but is attacked by strong acids, alkalis, and acid salts. Oxygen in solution accelerates the attack. When heated in air, tin forms SnO₂. It is, or was, used to plate steel, making "tin cans". Tin is used as one component in bell metals.

Isolation

Isolation: tHere is normally little need to isolate tin metal in the laboratory as it is readily available commercially. Tin is commonly available as the mineral cassiterite, SnO₂. Reduction of this dioxide with burning coal results in tin metal and was probably how tin was made by the ancients.

SnO₂ + 2C → Sn + 2CO

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