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Roger Weller, geology instructor

by Anna Montoya
Physical Geology
Fall 2012

                                                                                     Tin  (Sn)


Description: This is a blob of tin metal.


     Tin is a soft, flexible, silver-white (gray) metal. When a bar of tin is bent it makes a crackling sound, because it possesses a highly crystalline structure and also has a cubic structure.  When tin is warmed the color changes from gray to white and then possesses a tetragonal structure.  The transition from being in a crystalline structure and changing to the tetragonal structure is referred to as “Tin pest”.


     Tin does not easily oxidize (react with oxygen) and resists corrosion because it is surrounded by an oxide film.  The oxide film is formed on the surface of the metal (tin) as soon as the metal is exposed to oxygen.  Tin also resists corrosion when exposed to sea water, distilled water, or soft water.  Tin will corrode in some strong acids, alkalis, and acid salts.  Tin is used to coat other metals to prevent corrosion.


     Tin was first mined as far back as 3,500 BC in what we now call Turkey.  During 3,000 BC the first alloy in which tin was used was in bronze which is an alloy of tin and copper.  This discovery started the Bronze Age and lasted for about 2,000 years.  After 600 BC pewter was produced.  Pewter has an alloy of about 85% tin, and the remaining metals consisting of copper, and lead.  Tin cans were invented in 1810 to preserve food by a British Merchant named Peter Durand. 



     Tin is rarely used as a pure metal because it is too soft.  Therefore, tin is combined with other metals in order to make an alloy.  An alloy is defined as a mixture of metals.  Tin-plated steel containers were used widely for food preservation.  Tin alloys are used as solder for joining pipes or electric circuits, pewter, bronze, and dental fillings.  Tin alloy is also used in magnets, and tin oxide is used for ceramics and in gas sensors.  Tin foil was once a common wrapping material for foods.  Tin foil has been replaced by the use of aluminum foil.  Dyes, bleaching and pigment agents also contain tin.  Tin cans now usually have a polymer coating that prevents food from metal contact.  There is a tin alloy using zirconium and this alloy is used in nuclear reactors, which contains a small amount of tin.


Tin in the environment

     The amount of tin in the soil and in natural waters is very low.  The reason for this is that tin oxide is insoluble (not capable of being dissolved in liquid) and tin oxide strongly resists to weathering. 


Location of Tin

     Tin is mostly found deposited as silty sediments in flowing water and riverbeds.  Currently most of the world’s tin is produced in Malaysia, Bolivia, Indonesia, Thailand, Nigeria, England, and Australia.  There are no major tin deposits in the United States.  In some areas in Malaysia, tin and limestone are found together.  Tin is one of Malaysia’s successful forms of industry.  Here is a list of a few of the tin mines found in Malaysia:  Selangor, Perak, and Perlis.


Process of excavating Tin

     In countries like Malaysia a Tin Dredging machine was used to excavate tin.  Tin Dredging is defined as a floating factory, with a flat bottom, with sides and a roof on an artificial lake. It contains a heavy chain that consists of heavy buckets to scoop out sediments that are transported to the body of the dredge.


This is a picture of a tin dredging machine.

Description: Buckets

This is a picture of the heavy buckets that scoop out the sediments.


Health effects of Tin

     According to Wikipedia here is the definition for tin poisoning:  Tin poisoning refers to the toxic effects of tin and its compounds. Cases of poisoning from tin metal, its oxides, and its salts are "almost unknown"; on the other hand certain organotin compounds are almost as toxic as cyanide


     Acute tin poisoning, is the acute consumption of tin that may cause gastrointestinal problems, cramps, vomiting, nausea, and diarrhea.  Symptoms of chemical poisoning from tin can cause the following:   eye irritation, skin irritation, eye redness, eye soreness, respiratory problems, headaches, dizziness, severe sweating, breathlessness, and urination problems. 


     Long term effects of tin poisoning are:  depression, liver damage, malfunctioning of immune system, chromosomal damage, brain damage (causing anger, sleeping disorders, forgetfulness and headaches).  Tin is no longer used in tin cans because poisoning may have had effects from lead poisoning because lead was used to seal the top of tin cans.


How Tin effects the environment

     Tin is not toxic in its natural form but rather it is toxic in the organic form.  Tin constituents can continue to exist in the environment for long periods of time.  Tin constituents are not biodegradable.  On the other hand, organic tin can spread through the water system and it is known to cause harm to the aquatic ecosystem.  Organic tin is toxic to fungi, algae and phytoplankton.  Phytoplankton is an important link to the aquatic ecosystem as it provides other water organisms with oxygen. 


Medical testing for Tin Poisoning

Tin is ingested and absorbed through the gastrointestinal tract; therefore 80% of the tin will be excreted in urine.  Organic tin can be absorbed through the body.  Mildly elevated levels of Tin in the urine may reflect the sporadic dietary intake and excretion of tin.


Early signs of chronic organic tin excess cause some of the following symptoms:

1.     Headaches

2.     Reduced sense of smell

3.     Achy muscles

4.     Ataxia

5.     Vertigo

6.     Hyperglycemia

7.     Glucosuria

8.     Gastrointestinal tract problems


Organic tin exposure can also cause:

1.     Eye irritation

2.     Skin irritation

3.     Bronchial tube problems


     When one suspects tin poisoning, it is best to see your physician to determine the total body load.  Unfortunately there wasn’t much information about how to test for tin poisoning other than having a heavy metal toxicity testing performed.


     An additional research project is to be educated on the results of the polymers that are used for food preservation.  I found that the following polymers re used for that purpose and they are:  polyethylene terephthalate, polyvinyl chloride, a high density polyethylene and a low density polyethylene, and polystyrene.  I am currently not familiar with these chemicals and the hazards they may cause.