Tin

History

Sources

Properties

• 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 bent.
• 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.

Uses

• 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 food.
• 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 coatings.
• 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.

Handling

Costs