Element Tin, Sn Stannum, Poor Metal
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Tin History
Tin has been used, since epochs of Homer and Moses. It was discovered, probably, by accidental reducing of alluvial cassiterite (tin spar, tin stone). Alluvial aggradations are found much more often and may be processed much easier than other ores. Brythons were closely familiar with tin, as Cornwall slag hills testify. Tin metal, obviously, was hardly accessible, and very expensive: such conclusion has been made because of rarity of tin articles aming the Greek and Roman antiquity, despite tin is mentioned in the Fourth Book of Moses (Numbers) and the word cassitherite which means tin ore, is Greek-origin. Latin name Stannum or Stagnum came into use in Caesarian Rome. It is supposed that this word originated from Sanskrit stha (stand fast) or sthavan (firmly, sturdily).
Tin Occurrence
Tin is a typical element of Earth's crust upper levels; its crustal abundance is 2.5x10-4% by mass; in acid igneous rocks: 3x10-4%, in more deeply deposited basic rocks: 1.5x10-4%. Less tin is contained in mantle. Tin concentration is related to magmatic processes (as tin-enriched "tin-bearing" granites, pegmatites), as well as with hydrothermal processes. 23 of 24 tin minerals had been formed at high temperatures and under big pressure. Cassiterite SnO2 is commercially most important of them, the next is stannite (tin pyrite) Cu2FeSnS4. Tin migration in biosphere is sluggish, its abundance in seawater is only 3x10-7%. Some water plants accumulate tin; however, in general, it is dispersed.
Tin's role in living organisms is still behind the curtain. 1-2x10-4% of tin is contained in a human body; its consumption with food is limited by 0.2-3.5 mg. Tin vapour, dust and spray particles are very harmful. Inhalation or exposure to tin oxide may cause lung damage called stannosis or tin oxide pneumoconiosis. Some tinorganic compounds are highly toxic. Temporarily permissible level of tin compounds in atmosphere is 0.05 mg/m3, 200 mg/kg in food and 100 mg/kg. 2 g of tin is the toxic dose for human beings.
Tin Neighbours
Chemical Elements |