Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.
Tin is a member of Group 14 (IVA) in the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Tin is also part of the the carbon family. Other carbon family elements include carbon, silicon, germanium, and lead.
Tin is a highly workable metal that was once as valuable as silver for jewelry, coins, and special dishware. Today it is used as sheets in the construction of buildings and roofs, for soldering or joining metal parts, for storage containers, and in alloys like bronze and Babbitt metal.
Discovery and naming
Tin, its alloys, and its compounds have been known to humans for thousands of years. A number of references to the element can be found in the Bible. Tin was apparently known to other civilizations also. For example, the sacred Hindu book Rig Veda, written in about 1000 B.C., mentions tin among other metals known to the Hindus.
Group 14 (IVA)
The alloy of tin known as bronze was probably produced even earlier than the pure metal. An alloy is made by melting and mixing two or more metals. The mixture has properties that are different than any of the metals alone. The Egyptians, Mesopotamians, Babylonians, and Peruvians were producing bronze as far back as 2000 b.c. The alloy was probably discovered accidentally when copper and tin compounds were heated together. Over time, a method for producing consistent bronze was developed.
Bronze became popular among ancient peoples because it was harder and tougher than copper. Before the discovery of bronze, many metal items were made out of copper. But copper is soft and bends easily. Bronze is a much better replacement for copper in tools, eating utensils, and weapons. Bronze marked a significant advance in human civilization. This strong alloy improved transportation methods, food preparation, and quality of life during a period now known as the Bronze Age (4000—3000 b.c.).
The origin of the name tin is lost in history. Some scholars believe it is named for the Etruscan god Tinia. During the Middle Ages, the metal was known by its Latin name, stannum. It is from this name that the element's symbol, Sn, is derived.
The most common allotrope of tin is a silver-white metallic-looking solid known as the β-form (or "beta-form"). Allotropes are forms of an element with different physical and chemical properties. This "white tin" has a melting point of 232°C (450°F), a boiling point of 2,260°C (4,100°F), and a density of 7.31 grams per cubic centimeter.
One of tin's most interesting properties is its tendency to give off a strange screeching sound when it is bent. This sound is sometimes known as "tin cry." β-tin is both malleable and ductile. Malleable means capable of being hammered into thin sheets. Ductile means capable of being drawn into a thin wire. At temperatures greater than 200°C, tin becomes very brittle.
A second form of tin is α-tin (or "alpha-tin"), also known as "gray tin." Gray tin forms when white tin is cooled to temperatures less than about 13°C. Gray tin is a gray amorphous (lacking a crystalline shape) powder. The change from white tin to gray tin takes place rather slowly. This change is responsible for some peculiar and amazing changes in objects made from the element For example, tin and its alloys are used in jewelry, kitchenware, serving cups, and other metallic objects. When these objects are cooled below 13°C for long periods of time, the tin changes from a silvery, metallic material to a crumbly powder.
In the late nineteenth century, organ pipes in many cathedrals of Northern Europe were made of tin alloys. During the coldest winters, these pipes began to crumble as tin changed from one allotropic form to the other. The change was known as "tin disease." At the time, no one knew why this change occurred.
One of tin's most interesting properties is its tendency to give off a strange screeching sound when it is bent. This sound is sometimes known as "tin cry."
Tin is relatively unaffected by both water and oxygen at room temperatures. It does not rust, corrode, or react in any other way. This explains one of its major uses: as a coating to protect other metals. At higher temperatures, however, the metal reacts with both water (as steam) and oxygen to form tin oxide.
Similarly, tin is attacked only slowly by dilute acids such as hydrochloric acid (HCl) and sulfuric acid (H2SO4). Dilute acids are mixtures that contain small amounts of acid dissolved in large amounts of water. This property also makes tin a good protective covering. It does not react with acids as rapidly as do many other kinds of metals, such as iron, and can be used, therefore, as a covering for those metals.
Tin dissolves easily in concentrated acids, however, and in hot alkaline solutions, such as hot, concentrated potassium hydroxide (KOH). The metal also reacts with the halogens to form compounds such as tin chloride and tin bromide. It also forms compounds with sulfur, selenium, and tellurium.
Occurrence in nature
Tin is not very abundant in nature. It ranks about 50th on the list of elements most commonly found in the Earth's crust. Estimates are that the crust contains about 1 to 2 parts per million of tin.
By far the most common ore of tin is cassiterite, a form of tin oxide (SnO2). An ore is a compound or mixture from which an element can be extracted for commercial profit. Cassiterite has been mined for thousands of years as a source of tin. During ancient times, Europe obtained most of its tin from the British Isles. Today, the major producers of tin are China, Indonesia, Peru, Brazil, and Bolivia. The United States produces almost no tin of its own although it is the major consumer of the metal.
Tin has ten naturally occurring isotopes. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.
Fifteen radioactive isotopes have also been discovered. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.
None of the radioactive isotopes of tin have any commercial applications.
Tin can be produced easily by heating cassiterite with charcoal (nearly pure carbon). In this reaction, the carbon reacts with and removes oxygen from the cassiterite, leaving pure tin behind.
This reaction occurs so easily that people knew of the reaction thousands of years ago.
In order to obtain very pure tin, however, one problem must be solved. Iron often occurs in very small amounts along with tin oxide in cassiterite. Unless the iron is removed during the extraction process, a very hard, virtually unusable form of tin is produced. Modern systems of tin production, therefore, involve two steps. In one of those steps, impure tin is heated in the presence of oxygen to oxidize any iron in the mixture. In this reaction, iron is converted to iron(III) oxide, and metallic tin is left behind:
The largest amount of tin used in the United States goes to the production of solder. Solder is an alloy, usually made of tin and lead, with a low melting point. It is used to join two metals to each other. For example, metal wires are attached to electrical devices by means of solder. Solder is also used by plumbers to seal the joint between two metal pipes.
The largest amount of tin used in the United States goes to the production of solder.
Solder is often applied by means of a soldering iron. A soldering iron consists of a steel bar through which an electric current runs. The electric current heats the bar as it passes through it. When a small piece of solder is placed on the tip of the soldering iron, it melts. The solder is then applied to the joint between two metals. When it cools, the bond is strong. In 1996, 15,600 metric tons of tin were used in the production of solder.
Tin is also used in the manufacture of other alloys. Bronze, for example, is an alloy of tin and copper. In 1996, more than 2,750 metric tons of bronze were produced in the United States. It is used in a wide variety of industrial products, such as spark-resistant tools, springs, wire, electrical devices, water gauges, and valves.
One application of tin that was once important is in the manufacture of "tin foil." Tin foil is a very thin sheet of tin used to wrap candies, tobacco, and other products. The tin protected the products from spoiling by exposure to air. Today, most tin foil is actually thin sheets of aluminum because aluminum is less expensive.
A very important application of tin is tinplating. Tinplating is the process by which a thin coat of tin is placed on the surface of steel, iron, or another metal. Tin is not affected by air, oxygen, water, acids, and bases to the extent that steel, iron, and other metals are. So the tin coating acts as a protective layer.
Perhaps the best known example of tin plating is in the production of food cans. Tin cans are made of steel and are covered with a thin layer of tin. Most food and drink cans today are made out of aluminum because it is cheaper.
Metals can be plated with tin in one of two ways. First, the metal to be plated can simply be dipped in molten (liquid) tin and then pulled out. A thin layer of liquid tin sticks to the base metal and then cools to form a thin coating. The second method is electroplating. In the process of electroplating, the base metal is suspended in a solution of tin sulfate, or a similar compound. An electric current passes through the solution, causing the tin in the solution to be deposited on the surface of the base metal.
Tin was once important in the manufacture of "tin foil." Now, aluminum is used because it is less expensive.
Another tin alloy is Babbitt metal. Babbitt metal is a soft alloy made of any number of metals, including arsenic, cadmium, lead, or tin. Babbitt metal is used to make ball bearings for large industrial machinery. The Babbitt metal is laid down as a thin coating on heavier metal, such as iron or steel. The Babbitt metal retains a thin layer of lubricating oil more efficiently than iron or steel.
About a sixth of all tin consumed in the United States is used in the production of tin compounds. Some of the most important of those compounds and their uses are as follows:
M ost of today's toys are made of plastic. But until World War II (1939-45), most of the finest toys in the world were made of tin-plated metal. The earliest of these toys were made in the early 1800s. They were based on common objects and events, such as trains, horse-drawn carriages, sailing ships, and people from everyday life.
During the first half of the twentieth century, the most popular tin toy was the automobile. Toymakers made replicas of every type of car manufactured in the world. These toy cars ranged from the very simplest to the most detailed and elabrate.
Following World War II, plastic toys became much more popular, but tin toys were still made. Reflecting the times, these toys often represented space ships, robots, and other modern objects.
The manufacture of tin toys is no longer the large-scale business it was one hundred years ago. However, toy-collecting has remained a fascinating hobby for adults and children around the world. Some antique collectors and dealers specialize in tin toys.
tin chloride (SnCl2): used in the manufacture of dyes, polymers, and textiles; in the silvering of mirrors; as a food preservative; as an additive in perfumes used in soaps; and as an anti-gumming agent in lubricating oils
tin oxide (SnO2): used in the manufacture of special kinds of glass, ceramic glazes and colors, perfumes and cosmetics, and textiles; and as a polishing material for steel, glass, and other materials
tin chromate (SnCrO4 or Sn(CrO4)2): brown or yellowish-brown compounds used as a coloring agent for porcelain and china
tin fluoride (SnF2) and tin pyrophosphate (Sne2P2O7): used as toothpaste additives to help protect against cavities
Most compounds of tin are toxic (poisonous). Tin compounds are most likely to present a hazard when they get into the air. Then, they may be inhaled, after which they can cause problems such as nausea, diarrhea, vomiting, and cramps.
The U.S. government has set a standard of 2 milligrams per cubic meter of air for most tin compounds. For organic compounds of tin (those that contain the element carbon also), the Limit is 0.1 milligram per cubic meter. Miners and factory workers are the most likely people to be exposed to these levels of tin. The amount of tin absorbed from canned foods is too small to be of concern to consumers.
Tin is one of the basic chemical elements. When refined, it is a silvery-white metal known for its resistance to corrosion and its ability to coat other metals. It is most commonly used as a plating on the steel sheets used to form cans for food containers. Tin is also combined with copper to form bronze and with lead to form solder. A tin compound, stannous fluoride, is often added to toothpaste as a source of fluoride to prevent tooth decay.
The earliest use of tin dates to about 3500 b.c. in what is now Turkey, where it was first mined and processed. Ancient metalworkers learned to combine relatively soft copper with tin to form a much harder bronze, which could be made into tools and weapons that were more durable and stayed sharp longer. This discovery started what is known as the Bronze Age, which lasted about 2,000 years. The superiority of bronze tools spurred the search for other sources of tin. When extensive tin deposits were found in England, traders brought the precious metal to countries in the Mediterranean area, but kept the source a secret. It wasn't until 310 b.c. that the Greek explorer Pytheas discovered the location of the mines near what is now Cornwall, England. Much of the impetus for the Roman invasion of Britain in 43 a.d. was to control the tin trade. The chemical symbol for tin, Sn, is derived from the Latin name for the material, stannum.
Elsewhere in the world, tin was used in ancient China and among an unknown tribe in what is now South Africa. By about 2500-2000 b.c., metalworkers on the Khorat Plateau of northeast Thailand used local sources of tin and copper to produce bronze, and by about 1600 b.c. bronze plows were being used in what is now Vietnam. Tin was also known and used in Mexico and Peru before the Spanish conquest in the 1500s.
The use of tin as a plating material dates to the time of the Roman Empire, when copper vessels were coated with tin to keep them bright looking. Tinned iron vessels appeared in central Europe, in the 1300s. Thin sheets of iron coated with tin, called tinplate, became available in England during the mid-1600s and were used to make metal containers. In 1810, Pierre Durand of France patented a method of preserving food in sealed tinplate cans. Although it took many years of experimenting to perfect this new technique, tin cans began replacing bottles for food packaging by the mid-1800s.
In 1839, Isaac Babbitt of the United States invented an antifriction alloy, called Babbitt metal, which consisted of tin, antimony, and copper. It was widely used in bearings and greatly assisted the development of high-speed machinery and transportation.
In 1952, the firm of Pilkington in England revolutionized the glassmaking industry with the introduction of the "float glass" method for the continuous production of sheet glass. In this method, the molten glass floats on a bath of liquid, molten tin as it cools. This produces a very flat glass surface without the rolling, grinding, and polishing operations that were required prior to the introduction of this method.
Today, most of the world's tin is produced in Malaysia, Bolivia, Indonesia, Thailand, Australia, Nigeria, and England. There are no major tin deposits in the United States.
There are nine tin-bearing ores found naturally in the earth's crust, but the only one that is mined to any extent is cassiterite. In addition to the ores themselves, several other materials are often used to process and refine tin. These include limestone, silica, and salt. Carbon, in the form of coal or fuel oil, is also used. The presence of high concentrations of certain chemicals in the ore may require the use of other materials.
The process of extracting tin from tin ore varies according to the source of the ore deposit and the amount of impurities found in the ore. The tin deposits in Bolivia and England are located deep underground and require the use of tunnels to reach the ore. The ore in these deposits may contain about 0.8-1.0% tin by weight. Tin deposits in Malaysia, Indonesia, and Thailand are located in the gravel along streambeds and require the use of dredges or pumps to reach the ore. The ore in these deposits may contain as little as 0.015% tin by weight. Over 80% of the world's tin is found in these low-grade gravel deposits.
Regardless of the source, each process consists of several steps in which the unwanted materials are physically or chemically removed, and the concentration of tin is progressively increased. Some of these steps are conducted at the mine site, while others may be conducted at separate facilities.
Here are the steps used to process the low-grade ore typically found in gravel deposits in Southeast Asia:
- 1 When the gravel deposits are located at or below the water level in the stream, they are brought up by a floating dredge, operating in an artificial pond created along the streambed. The dredge excavates the gravel using a long boom fitted either with chain-driven buckets or with a submersed rotating cutter head and suction pipe. The gravel passes through a series of revolving screens and shaker tables onboard the dredge to separate the soil, sand, and stones from the tin ore. The remaining ore is then collected and transferred ashore for further processing.
In the 1800s, tin was an ordinary household material particularly popular with the working class because of its low cost and bright luster. Made of iron or steel rolled thin and dipped in molten tin, it was easy to manipulate, cut, and solder. Tin was used for nearly everything that copper, pewter, brass, or silver could be used for, but generally did not last as long. Reviewing tin catalogs from about 1870 reveals that tin was used for far more than cookie cutters—it was used to make children's toys, coffeepots, lunch boxes, and even gentlemen's spitoonsl
However, it was also popularly used to produce a gift for the tenth anniversary, called the "tin anniversary." While not as well-known as the twenty-fifth, which requires silver gifts, the Victorian housewife knew she might well receive a tenth anniversary gift of tin like the tin bonnet depicted here. Shaped in the form of a "spoon bonnet" popular about 1870, it is likely that this piece dates to that time. Certainly, it can't be worn, but was meant to be displayed on a shelf as a remembrance of that anniversary. Tinsmiths provided whimsical gifts just for this purpose. Museum collections include not only hats but tin shoes and decorative vases that could never be used to hold water.
Nancy EV Bryk
When the gravel deposits are located in dry areas at or above the water level in the stream, they are first broken up with jets of water pumped through large nozzles. The resulting muddy slurry is trapped in an artificial pond. A pump located at the lowest point in the pond pumps the slurry up into a wooden trough, called a palong, which has a gentle downward slope along its length. The tin ore, which is heavier than the sand and soil in the mud, tends to sink and is trapped behind a series of wooden slats, called riffles. Periodically the trapped ore is dumped from the palong and is collected for further processing.
- 2 The ore enters the cleaning or dressing shed adjacent to the mining operation. First, it passes through several vibrating screens to separate out coarser foreign materials. It may then pass through a classifying tank filled with water, where the ore sinks to the bottom while the very small silt particles are carried away. It may also pass through a floatation tank, where certain chemicals are added to make the tin particles rise to the surface and overflow into troughs.
- 3 Finally the ore is dried, screened again, and passed through a magnetic separator to remove any iron particles. The resulting tin concentrate is now about 70-77% tin by weight and consists of almost pure cassiterite.
- 4 The tin concentrate is placed in a furnace along with carbon in the form of either coal or fuel oil. If a tin concentrate with excess impurities is used, limestone and sand may also be added to react with the impurities. As the materials are heated to about 2550° F (1400° C), the carbon reacts with the carbon dioxide in the furnace atmosphere to form carbon monoxide. In turn the carbon monoxide reacts with the cassiterite in the tin concentrate to form crude tin and carbon dioxide. If limestone and sand are used, they react with any silica or iron present in the concentrate to form a slag.
- 5 Because tin readily forms compounds with many materials, it often reacts with the slag. As a result, the slag from the first furnace contains an appreciable amount of tin and must be processed further before it is discarded. The slag is heated in a second furnace along with additional carbon, scrap iron, and limestone. As before, crude tin is formed and recovered along with a certain amount of residual slag.
- 6 The residual slag from the second furnace is heated one more time to recover any tin that has formed compounds with iron. This material is known as the hard head. The remaining slag is discarded.
- 7 The crude tin from the first furnace is placed in a low-temperature furnace along with the crude tin recovered from the slag plus the hard head. Because tin has a melting temperature much lower than most metals, it is possible to carefully raise the temperature of the furnace so that only the tin melts, leaving any other metals as solids. The melted tin runs down an inclined surface and is collected in a poling kettle, while the other materials remain behind. This process is called liquidation and it effectively removes much of the iron, arsenic, copper, and antimony that may be present.
- 8 The molten tin in the poling kettle is agitated with steam, compressed air, or poles of green wood. This process is called boiling. The green wood, being moist, produces steam along with the mechanical stirring of the poles. It was from this crude, but effective use of wood poles that the poling kettle got its name. Most of the remaining impurities rise to the surface to form a scum, which is removed. The refined tin is now about 99.8% pure.
- 9 For applications requiring an even higher purity, the tin may be processed further in an electrolytic refining plant. The tin is poured into molds to form large electrical anodes, which act as the positive terminals for the electrorefining process. Each anode is placed in an individual tank, and a sheet of tin is placed at the opposite end of the tank to act as the cathode, or negative terminal. The tanks are filled with an electrically conducting solution. When an electrical current is passed through each tank, the tin is stripped off the anode and is deposited on the cathode. The remaining impurities, which are generally bismuth and lead, fall out of the solution and form a slime at the bottom of the tank.
- 10 The cathodes are remelted, and the refined tin is cast in iron molds to form ingots or bars, which are then shipped to the various end users. Lower purity tin is usually cast into ingots weighing 25-100 lb (11-45 kg). Higher purity tin is cast into smaller bars weighing about 2 lb (1 kg).
The processes described have been proven to consistently produce tin at 99% purity and higher. To ensure this purity, samples are analyzed at various steps to determine whether any adjustments to the processes are required.
In the United States, the purity levels for commercial grades of tin are defined by the American Society for Testing Materials (ASTM) Standard Classification B339. The highest grade is AAA, which contains 99.98% tin and is used for research. Grade A, which contains 99.80% tin, is used to form tinplate for food containers. Grades B, C, D, and E are lesser grades ranging down to 99% purity. They are used to make general-purpose tin alloys such as bronze and solder.
There are no useful byproducts produced from tin processing.
Waste products include the soil, sand, and stones that are rejected during the mining and concentrating operations. These constitute a huge amount of material, but their environmental impact depends on the local disposal practices and the concentrations of other minerals that may be present. The slag produced during the smelting and refining operations is also a waste product. It may contain quantities of arsenic, lead, and other materials that are potentially harmful. Tin itself has no known harmful effects on humans or the environment.
The use of tin is expected to grow as new applications are developed. Because tin has no known detrimental effects, it is expected to replace other more environmentally harmful metals such as lead, mercury, and cadmium. One new application is the formulation of tin-silver solders to replace tinlead solders in the electronics industry. Another application is the use of tin shot to replace lead shot in shotgun shells.
Development work is underway to create a tin-based compound for use in refuse disposal landfill sites. This compound will interact with heavy metals, such as lead and cadmium, to prevent rain water from carrying them into the surrounding soil and water table.
Where to Learn More
Brady, George S., Henry R. Clauser, and John A. Vaccari. Materials Handbook, 14th Edition. McGraw-Hill, 1997.
Heiserman, David L. Exploring Chemical Elements and Their Compounds. TAB Books, 1992.
Hornbostel, Caleb. Construction Materials, 2nd Edition. John Wiley and Sons, Inc., 1991.
Kroschwitz, Jacqueline 1. and Mary Howe-Grant, ed. Encyclopedia of Chemical Technology, 4th edition. John Wiley and Sons, Inc., 1993.
Stwertka, Albert. A Guide to the Elements. Oxford University Press, 1996.
"Bronze Age Mine Found in Turkey," Science News (January 15, 1994): 46.
International Tin Research Institute. http://www.itri.co.udk.
Tin makes up only about 0.001 percent of the earth's crust, but it was well known in the ancient world. Named after the Etruscan god Tinia, tin has the symbol Sn, which comes from the Latin word for tin, stannum, which is related to the word stagnum (dripping), because tin melts easily. Tin is primarily obtained from the mineral cassiterite (SnO2) and is extracted by roasting cassiterite in a furnace with carbon.
Tin is a soft, pliable metal , but it is not used as such, because below 13°C, it slowly changes to a different allotype and forms a powder. Steel is plated with tin to make cans for food, and tin is also used in solders. Some tin compounds have been employed as antifouling agents in paint for ships and boats to prevent barnacles. However, even at low concentrations, these compounds are deadly to marine life, especially to oysters. Tin is thought to be an essential element for some living things, and this may also be true for humans.
A major use of tin has been as a constituent of alloys —such as bronze (tin and copper); pewter (tin and lead); superconducting wire (tin and niobium); Babbitt metal (tin, copper, and antimony); Bell metal (tin and copper); and fusible metal (tin, bismuth, and lead).
Stannous fluoride (SnF2), a compound of tin and fluorine, is used in some toothpastes to decrease the incidence of caries.
George H. Wahl Jr.
ChemGlobe. Available from <http://www.vcs.ethz.ch/chemglobe/ptoe/_/50.html>.
Jefferson Lab. "It's Elemental: The Element Tin." Available from <http://education.jlab.org/itselemental/ele050.html>.
Royal Society of Chemistry. "Visual Elements: Tin." Available from <http://www.chemsoc.org/viselements/pages/tin.html>.
tin / tin/ • n. 1. a silvery-white metal, the chemical element of atomic number 50. (Symbol: Sn) ∎ short for tinplate. 2. a metal container, in particular: ∎ chiefly Brit. another term for tin can: she had opened a tin of beans. ∎ a lidded airtight container made of tinplate or aluminum: Albert got out the cookie tin. ∎ chiefly Brit. an open metal container for baking food: grease a loaf tin. • v. (tinned / tind/ , tin·ning ) [tr.] cover with a thin layer of tin: the copper pans are tinned inside. PHRASES: have a tin ear be tone-deaf.
have a tin ear be tone-deaf.
little tin god a person, especially a minor official, who is pompous and self-important; an object of unjustified veneration or respect.
tin Lizzie in North America, a dated informal expression for a motor car, in particular a very early Ford.
Tin Man in the story of the Wizard of Oz, one of Dorothy's companions in the search for the magician.
Tin Pan Alley the name given to a district in New York (28th Street, between 5th Avenue and Broadway) where many songwriters, arrangers, and music publishers were formerly based. The phrase is now used for the world of composers and publishers of popular music, particularly with reference to the works of such composers as Irving Berlin, Jerome Kern, George Gershwin, Cole Porter, and Richard Rodgers.
tin wedding in the US, a 10th wedding anniversary.