Originally known in Latin as plumbum candidum (white lead), tin is a soft white metal with an unusually low melting pint of 231.85 degrees Celsius. Its chemical symbol, Sn, comes from its more recent Latin name, stannum, while the English name, tin, comes from a Germanic root.
History of Tin
Tin was known to ancient civilisations. Tin artefacts have been found in an Egyptian tomb of the eighteenth dynasty (1580-1350 BC), and it was traded around the Mediterranean by the Phoenicians who obtained it from Spain, Brittany and Cornwall. In the 19th century, Cornwall was the major producer of the metal, but then deposits were found in Bolivia and East Asia, and today China is the leading producer, followed by Indonesia and Peru.
Production of Tin
The metal is produced by smelting the ore, which is cassiterite, made up of tin(IV) oxide (SnO2). This ore is treated to remove sulfides of lead, bismuth, antimony, zinc, silver copper and iron, and then smelted in either a blast furnace or a reverberatory furnace with coke or anthracite to produce liquid tin. It is then refined either pyrolytically or electrolytically.
Chemical Properties of Tin
Tin is found in group IV of the Periodic Table with carbon, silicon, germanium and lead. It exhibits the oxidation states +2 and +4. In the +2 state, it is basic and behaves like a metal. In its +4 state, it is amphoteric and can behave in an acidic manner in alkaline solution. Tin(II) chloride (stannous chloride) is a reducing agent, while tin (IV) chloride (stannic chloride) is amphoteric. Organotin compounds or stannanes are organic compounds like diethyltin diiodide. They have a high toxicity and have been used as biocides, but their use is being phased out.
Uses of Tin
The most common application of tin is its use in alloys, and in tin plate, a thin sheet of steel with a protective coating of tin. Tin plate is used for food cans because it is not reactive to the acids present in food. Alloys of tin include bronze (tin and copper), pewter (tin and lead), superconducting wire (tin and niobium), Babbitt metal (tin, copper and antimony), bell metal (tin and copper and solder [tin and lead]). Babbitt metal is used for the surface of bearings. Superconducting wires are used in the manufacture of extremely powerful magnets.
Molten tin is used in the process of making float glass, in which molten glass is floated on the surface of molten tin, creating a sheet of uniform thickness and with very flat surfaces. The metal also used to be used for wrapping food, and, although it has been replaced by aluminum foil, this product is still often known as 'tin foil'.
Sources
- John Emsley, Molecules at an Exhibition, Oxford University Press, 1998, p51
- Dr JB Calvert, Tin, University of Denver (accessed 29th April 2011)
Simon Davies - Simon Davies has lived a varied life so far After completing a BSc in Chemistry at the University of Bristol, UK, he worked as a ...
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