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Element Tin, Sn Stannum, Poor Metal

History of Tin

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).

The use of tin as a constituent of bronze dates back to prehistoric times. The age of bronze, which in some countries intervened between the age of stone and that of iron, is considered by Montelius to date back in the case of Britain to 2500 b.c. The " tin " of the Old Testament, which is a translation of the Hebrew word bedhil and appears as the Greek word κασσιτερος in the Septuagint, is probably a copper-tin alloy which was known in Egypt in 1600 b.c.

Ancient bronze was an alloy of copper with a little tin, and was employed by the Greeks for coinage till 400 b.c., when the tin began to be displaced by lead. About the Christian era the word κασσιτερος, which is probably connected with the Arabic " Kasdir," meaning tin, came to be applied to this metal; so the British Isles, whence Julius Caesar brought tin, were called the Cassiterides. Tin was also known about this time as plumbum album or candidum, in contradistinction to lead, which was plumbum nigrum; and Caesar has the following passage about this metal in Bellum gallicum, " Nascitur ibi (in Britannia) plumbum album in mediis regionibus, in maritimis ferrum, sed eius exigua est copla; aere utuntur importato "; whilst Pliny 1 thus describes the source of the metal: "Ex adverso Celtiberiae complures sunt insulae, Cassiterides dictae graecis, a fertilitate plumbi."

The Phoenicians are said to have brought tin from the Cassiterides; and during the Roman occupation of Britain tin was taken from the Cornish mines across to Iktis or St. Michael's Mount at low water, whence it was shipped to Gaul and carried via Marseilles to Italy; it was also obtained about the same time from Spain and Portugal. It would appear from the names applied to tin and lead that these metals were recognised as distinct species; that they were regarded, however, rather as varieties of one metal is shown by the following passage of Pliny: " Sequitur naturae plumbi cujus duo genera, nigrum atque candidum." The word stannum is found in the writings of Pliny, but it appears to have been used at that time, not for tin, but for lead and its alloys; it was first applied to tin in the fourth century of our era. Some interesting information concerning the preparation and uses of tin is contained in a Greek papyrus of the third century, discovered at Thebes and preserved in the Museum of Antiquities at Ley den. In the Latin works of the thirteenth century which are professedly translations of the Arabian alchemist Geber (b. a.d. 765) some important properties of metallic tin are mentioned, such as its " cry " and its power of imparting brittleness to alloys. On account of this latter property tin was called by the Western alchemists diabolus metallorum. Tin was one of the original metals associated by the "alchemists with Greek mythology. By the Greek alchemists it was termed Hermes; but later, about the beginning of the sixth century, it was identified with Zeus or Jupiter, and received the sign \xE2\x99\x83.\n

Occurrence of Tin

Tin is a typical element of Earth's crust upper levels; its crustal abundance is 2.5×10-4% by mass; in acid igneous rocks: 3×10-4%, in more deeply deposited basic rocks: 1.5×10-4%. 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. 1-2×10-4% 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.\n


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