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 Tin 

Notable Characteristics

Tin is a malleable, ductile, highly crystalline, silvery-white metal whose crystal structure causes a "tin cry" when a bar of tin is bent (caused by crystals breaking). This metal 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 Sn2 is when it is heated in the presence of air. Sn2, in turn, is feebly acidic and forms stannate (tin) 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. Tin is malleable at ordinary temperatures but is brittle when it is heated.

Allotropes

Solid tin has two allotropes at normal pressure. At low temperatures it exists as gray or alpha tin, which has a cubic crystal structure similar to silicon and germanium. When warmed above that 13.2 °C it changes into white or beta tin, which is metallic and has a tetragonal structure. It slowly changes back to the gray form when cooled, which is called the tin pest or tin disease. However, this transformation is affected by impurities such as aluminum and zinc and can be prevented from occurring through the addition of antimony or bismuth.

Applications

Tin bonds readily to iron, and has been used for coating lead or zinc and steel to prevent corrosion. Tin-plated steel containers are widely used for food preservation, and this forms a large part of the market for metallic tin. Other uses;

Crystalline tin-niobium alloy is superconductive at very low temperatures and has been studied for use in the production of superconductive magnets[?] that can generate very strong magnetic field strengths while using very little power. These magnets, which are made of tin-niobium wire, weigh only a couple of kilograms and can make magnetic fields using power from a small battery that are comparable to those made by a 100 ton electromagnet using a large power supply.

History

Tin (anglo-Saxon, tin, 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 thriving tin trade existed in Classical times between the mines in Cornwall and the civilizations of the Mediterranean. However the pure metal was not used until about 600 BC.

Occurrence

About 35 countries mine tin throughout the world. Nearly every continent has an important tin-mining country. Tin is produced by reducing the ore with coal in a reverberatory furnace[?]. This metal is a relatively scarce element with an abundance in the earth's crust of about 2 ppm, compared with 94 ppm for zinc, 63 ppm for copper, and 12 ppm for lead. Most of the world's tin is produced from placer[?] deposits; at least one-half comes from Southeast Asia. The only mineral of commercial importance as a source of tin is cassiterite[?] (SnO2), although small quantities of tin are recovered from complex sulfides[?] such as stanite[?], cylindrite[?], frankeite[?], canfieldite[?], and teallite[?]. Secondary, or scrap, tin is also an important source of the tin.

Isotopes

Ordinary tin is made of nine stable isotopes and there are 18 unstable isotopes in addition to this that are also known.

Precautions

The small amount of tin that is found in canned foods isn't harmful to humans. Trialkyl[?] and triaryl[?] tin compounds are biocides and need to be handled with care.

External Links

See also: International Tin Council, tinned[?]

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