Brief introduction of metal tin


Tin is one of the metals discovered early in the ancient times. In the nature, tin is not existed in the elemental state and it is also discovered a little later than copper. It is a kind of metal with low melting point which makes it into the main components of solders.

Tin has three kinds of allotropes which are white tin, grey tin and creep tin. Tin can exist in different crystalline state under different environment. White tin is a kind of wrought metal and has the most stable form among three kinds of tin under room temperature and higher than the room temperature. When the temperature is below 13 degrees Celsius, tin crystal lattice will be rearranged and the space between atoms will be enlarged, thus will form a new kind of crystal habit-the grey tin. When grey tin lose its metallic character, it will become a kind of semiconductor. The internal stress generated by the contact between different crystal lattice will make metal tin fragmented into powders. The tansformation speed of crystal habit will become fast at the low temperature of surrounding medium, which will become fastest at 33 degrees Celsius below zero: when the temperature is below zero, white tin will lose its gloss and turn into dark grey and eventually fragmented into powders. We call this phenomenon as “tin pest”. Besides, tin plates that are not infected with “tin pest” will generate grey spots and gradually “rotten” once contacted with those tin plates having “tin pest”. Scientists have found the substance to prevent “tin pest”, among which there is a kind of metal called bismuth. The redundant electron in bismuth atoms can provide crystal lattice for tin and stabilize the state of tin, thus will completely eliminate the emergence of “tin pest”.

Tin alloy containing 52 percents of bismuth, 32 percents of lead and 16 percents of tin has the melting point of only 95 degrees Celsius and can be smelted in boiled water. However, the melting point of tin is 232 degrees Celsius; bismuth is 271 degrees Celsius; lead is 327 degrees Celsius. The alloy melting point is much lower than that of each kind of pure metal which compose it. The melting point of tin alloy containing gallium and indium is even lower, among which one of the melting point is 10.6 degrees Celsius. Low melting point alloy can be used as electric fuse.

Stannous chloride and stannic oxide can be made into mordant for cotton cloth and silk. Besides, stannous chloride can be used as the reducing agent and decolorising agent and can be used in tinplating for electroplate. In order to paint the porcelain and glass with red, we can use a kind of cudbear called Cassius which is formed at the time of adding stannous chloride into gold chloride solution. Tin sulphate, same with mosaic gold, can be used as the gold pigment.

White tin can be made into housewares and can also be coated on the surface of copper and iron. The metal plate coated with tin is often called “tinplate” on which the tin layer will protect the iron from corrosion. Once the tin layer is damaged, the corrosion speed of iron will become fast. This is because iron is more active than tin, and iron together with tin will form the primary battery when both contacting with electrolyte solution, in which the iron will be gradually oxidized as the cathode of primary battery. This phenomenon is called electrochemical corrosion in chemistry.

Tin is a kind of metal with tiny toxicity. Tin salts are completely harmless to human body and will not produce hazardous substance after contacting with food, which can also resist to the corrosion of oxygen, water and organic acid. This performance of tin is fully used, which reflects in that currently about the half of the world’s total output of tin are used in producing tin cans and a very thin layer of tinplate can be used in storing millions of tons meat, fish, fruits and vegetables. Therefore, tin deservedly won the title of “can metal”.

After carrying out a great deal of analysis and repeated experiments, scientists confirmed the conclusion that there might be tin ore existed due to the presence of fluorine. In the prehistoric period, tin existed in a complex substance form in which fluorine is a necessary composition. Afterwards, tin and tin compounds gradually formed a kind of sediment which is the subsequent deposit, while fluorine is stranded near the sediment. This discovery not only helps to measure the distribution areas of tin, but also helps to predict the size of tin reserves.