stannic oxide


Tin is a chemical element with the symbol Sn (stannum) and atomic number 50. This silvery, malleable poor metal that is not easily oxidized in air and resists corrosion, is found in many alloys and is used to coat other metals to prevent corrosion. Tin is obtained chiefly from the mineral cassiterite, where it occurs as an oxide. It can be alloyed with copper to make bronze. Pewter alloys contain from 85% up to 99% tin.


Tin is a malleable, ductile, highly crystalline, silvery-white metal; when a bar of tin is bent, a strange crackling sound, known as the tin cry, can be heard due to the twinning of the crystals. Tin is malleable at ordinary temperatures but is brittle when it is cooled.


Tin resists corrosion from distilled, sea and soft tap water, but can be attacked by strong acids, alkalis, and by acid salts. Tin acts as a catalyst when oxygen is in solution and helps accelerate chemical attack. Tin forms the dioxide SnO2 when it is heated in the presence of air. SnO2, in turn, is feebly acidic and forms stannate (SnO32-) salts with basic oxides. Tin can be highly polished and is used as a protective coat for other metals in order to prevent corrosion or other chemical action. This metal combines directly with chlorine and oxygen and displaces hydrogen from dilute acids.




Although the transformation temperature is 13.2 °C, the change does not take place unless the metal is of high purity, and only when the exposure temperature is well below 0 °C. This process is known as tin disease or tin pest. Tin pest was a particular problem in northern Europe in the 18th century as organ pipes made of tin alloy would sometimes be affected during long cold winters. Some sources also say that during Napoleon's Russian campaign of 1812, the temperatures became so cold that the tin buttons on the soldiers' uniforms disintegrated, contributing to the defeat of the Grande Armée. The veracity of this story is debatable, because the transformation to gray tin often takes a reasonably long time. Commercial grades of tin (99.8%) resist transformation because of the inhibiting effect of the small amounts of bismuth, antimony, lead, and silver present as impurities. Alloying elements such as copper, antimony, bismuth, cadmium, and silver increase its hardness. Tin tends rather easily to form hard, brittle intermetallic phases, which are often undesirable. It does not form wide solid solution ranges in other metals in general, and there are few elements that have appreciable solid solubility in tin. Simple eutectic systems,however, occur with bismuth, gallium, lead, thallium, and zinc.


Tin (Old English: tin, Old Latin: plumbum candidum ("white lead"), Old German: tsin, Late Latin: stannum) is one of the earliest metals known and was used as a component of bronze from antiquity. Because of its hardening effect on copper, tin was used in bronze implements as early as 3,500 BC. A shipwreck at Uluburun, Turkey dating to 1336 BC contains a shipment of tin, perhaps originating in Afghanistan. European tin mining is believed to have started in Cornwall and Devon (esp. Dartmoor) in Classical times, and a thriving tin trade developed with the civilizations of the Mediterranean. However the lone metal was not used until about 600 BC. The last Cornish tin mine, at South Crofty near Camborne, closed in 1998 bringing 4,000 years of mining in Cornwall to an end, but as of 2007 increased demand from China may lead to its re-opening.

The word "tin" has cognates in many Germanic and Celtic languages. The American Heritage Dictionary speculates that the word was borrowed from a pre-Indo-European language. The later name "stannum" and its Romance derivatives come from the lead-silver alloy of the same name for the finding of the latter in ores; the former "stagnum" was the word for a stale pool or puddle.

In modern times, the word "tin" is often improperly used as a generic phrase for any silvery metal that comes in sheets. Most everyday materials that are commonly called "tin", such as aluminium foil, beverage cans, corrugated building sheathing and tin cans, are actually made of steel or aluminium, although tin cans (tinned cans) do contain a thin coating of tin to inhibit rust. Likewise, so-called "tin toys" are usually made of steel, and may or may not have a coating of tin to inhibit rust. The original Ford Model T was known colloquially as the Tin Lizzy.

Historical Cornwall was the major tin producer, this changed after large amounts of tin have been found in the Bolivian tin belt and the east asian tin belt stretching from China through Thailand and Laos to Malaya and Indonesia. The tin produceres founded in 1931 the International Tin Comittee followed in 1956 by the International Tin Council a institution to control the tin market. After the collapse of the market in October 1985 the price for tin nearly halved.


In 2007, the People's Republic of China was the largest producer of tin, where the tin deposites are concentrated in the southeast Yunnan tin belt, with 43% of the world's share, followed by Indonesia and Peru, reports the USGS.


Tasmania hosts some deposits of historical importance, most notably Mount Bischoff and Renison Bell. New deposits are also reported to be in southern Mongolia.

It is estimated that, at current consumption rates, the Earth will run out of tin in 40 years. However Lester Brown has suggested tin could run out within 20 years based on an extremely conservative extrapolation of 2% growth per year. However this is offset by the increased use of secondary, or scrap tin, as a readily available source of the metal.

See also Tin minerals


Metall and Alloy


  • Tin is used extensively for alloys, some important tin alloys are bronze, bell metal, Babbitt metal, die casting alloy, pewter, phosphor bronze, soft solder, and White metal.


  • For a long time the antifouling property of organotin compounds was used for the preservation of wood and to prevent growth of marine organisms on ships. Tributyltin was used as additive for ship paint. The use declined after organotin compounds where recognised as persistent organic pollutants with a extremly high toxicity for some marine organism, for example dog whelk. The EU banned the use of organotin compounds in 2003.
  • Tin is added to some dental care products as stannous fluoride (SnF2). Stannous fluoride can be mixed with calcium abrasives while the more common sodium fluoride gradually becomes biologically inactive combined with calcium. It has also been shown to be more effective than sodium fluoride in controlling gingivitis.


For discussion of Stannate compounds (SnO32−) see Stannate. For Stannite (SnO2) see Stannite. See also Stannous hydroxide (Sn(OH)2), Stannic acid (Stannic Hydroxide - Sn(OH)4), Tin dioxide (Stannic Oxide - SnO2), Tin(II) oxide (Stannous Oxide - SnO), Tin(II) chloride (SnCl2), Tin(IV) chloride (SnCl4)

See also Tin compounds


Tin is the element with the greatest number of stable isotopes (ten), which is probably related to the fact that 50 is a "magic number" of protons. 28 additional unstable isotopes are known, including the "doubly magic" tin-100 (100Sn) (discovered in 1994).


Tin plays no known natural biological role in humans, and possible health effects of tin are a subject of dispute. Tin itself is not toxic but most tin compounds are.

Triorganotins are very toxic. Tri-n-alkyltins are phytotoxic and depending on the organic groups, they can be powerful bactericides and fungicides. Other triorganotins are used as miticides and acaricides.

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