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|Atomic Number:||50||Atomic Symbol:||Sn|
|Atomic Weight:||118.69||Electron Configuration:||2-8-18-18-4|
|Melting Point:||231.9oC||Boiling Point:||2270oC|
|Description:||Very malleable white metal|
|Uses:||Used as a coating for steel cans. Also in solder, bronze and
pewter. Stannous flouride, a compound of tin and flourine is used in toothpaste.|
History(anglo-Saxon, tin; L. stannum) Known to the ancients.
SourcesTin is found chiefly in cassiterite (SnO2). Most of the world's
supply comes from Malaya, Bolivia, Indonesia, Zaire, Thailand, and Nigeria. The
U.S. produces almost none, although occurrences have been found in Alaska and
California. Tin is obtained by reducing the ore withcoal in a reverberatory
furnace. Ordinary tin is composed of nine stable isotopes; 18 unstable isotopes
are also known.
- Ordinary tin is a silver-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
- The element has two allotropic forms at normal pressure.
- On warming, gray, or alpha tin, with a cubic structure, changes at 13.2C
into white, or beta tin, the ordinary form of the metal.
- White tin has a tetragonal structure.
- When tin is cooled below 13.2C, it changes slowly from white to gray.
- This change is affected by impurities such as aluminum and zinc, and can be
prevented by small additions of antimony or bismuth.
- This change from the alpha to beta form is called the tin pest.
- There are few if any uses for gray tin.
- Tin takes a high polish and is used to coat other metals to prevent
corrosion or other chemical action.
- Such tin plate over steel is used in the so-called tin can for preserving
- Alloys of tin are very important.
- Soft solder, type metal, fusible metal, pewter, bronze, bell metal, Babbitt
metal, White metal, die casting alloy, and phosphor bronze are some of the
important alloys using tin.
- 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, which is feebly acid, forming stannate
salts with basic oxides.
- The most important salt is the chloride, which is used as a reducing agent
and as a mordant in calico printing.
- Tin salts sprayed onto glass are used to produce electrically conductive
- These have been used for panel lighting and for frost-free windshields.
- Most window glass is now made by floating molten glass on molten tin (float
glass) to produce a flat surface (Pilkington process).
- Of recent interest is a crystalline tin-niobium alloy that is
superconductive at very low temperatures.
- This promises to be important in the construction of superconductive magnets
that generate enormous field strengths but use practically no power.
- Such magnets, made of tin-niobium wire, weigh but a few pounds and produce
magnetic fields that, when started with a small battery, are comparable to that
of a 100 ton electromagnet operated continuously with a large power supply.
HandlingThe small amount of tin found in canned foods is quite
The agreed limit of tin content in U.S. foods is 300 mg/kg.
trialkyl and triaryl tin compounds are used as biocides and must be handled
CostsOver the past 25 years the price of tin has varied from 50
cents/lb to its present price of about $4/lb. as of January 1990.