Category Metal & Non-Metals

The ancient Roman Empire is known for its magnificent wealth and rich culture. Despite all their glory, many Romans died young. After scientific enquiries, it was concluded that many Romans died young because of poisoning. This happened because they used one metal without knowing about its hazardous effects.

Lead was one of the most popular elements in ancient Rome. They used plates and vessels made of lead. Even water pipes were made of lead. The water in the pipes reacted with lead to form lead carbonate, capable of causing many chronic diseases. Many people died of various ailments and the Empire steadily declined, all without the Romans having any idea of what went wrong.

Of course, there were other reasons too for the decline of the Roman Empire, but it is still believed that lead played an important role in its downfall and collapse.

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Lead is of great use in the production of many products. For decades, it was added to paint to make it last longer and flow easier. Lead was included in fuel to make engines run better. We even used to manufacture water pipes made of lead.

Solder was also made with a lot of lead in it because it melted at a low temperature, and was much easier to use. These are but a few uses of lead. Yet, the use of lead is not encouraged much nowadays. Want to know why?

Though lead is useful, it is a poisonous metal. Even tiny amounts of lead can harm you. Inhaling lead can cause severe stomach ache and consumption of even the tiniest amount of this deadly metal is enough to paralyze you. Young children who breathe or swallow lead suffer brain damage, and become deaf and blind. Therefore, today, we have strict rules for controlling the use of lead.

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Let us now look at the various uses of tin. Tin is used to coat other metals to prevent corrosion. It is an alloying agent. Some of the important tin alloys include soft solder, type metal, fusible metal, pewter, bronze, bell metal, Babbitt metal, white metal, die casting alloy, and phosphor bronze.

Tin is used for making window glasses. The glasses used for making the windows of your classroom and houses are made by using a process which involves floating molten glass on molten tin to produce a flat pane surface. Tin salts are sprayed onto glass to produce electrically conductive coatings. These salt treated panes can be used for panel lighting and for frost-free wind-shields.

Tin is also used to make agricultural goods like fungicides. Some compounds of tin are very useful in the manufacture of paints. Tin is also used to make superconductive magnets that generate enormous field strengths, but use practically no power.

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All of us use tins at our homes. Tins are air-tight containers made of thin metal. If you go to the supermarkets, you would find shelves in the food section loaded with cans of preserved food. What are these tins made of? Tin cans are not made solely of tin, but rather tin-coated steel or tinplate. The properties of tin make it ideal for making cans. Therefore tin is known as canning material.

Tin does not react with oxygen, water, or the acids in food and its salts are completely harmless to humans. This is why millions of tons of meat, fish, fruits and vegetables are preserved in tin cans.

The mining of tin is believed to have begun around Classical times, in Cornwall and Devon. Within the civilizations of the Mediterranean, a thriving tin trade developed, and to this day, tin plays a very important role in our lives, directly and indirectly.

Tin is rarely found in its free form in nature. To obtain tin, tin ores have to be smelted first. Tin oxide or cassiterite is one of the main ores of tin. Let us now take a look at how tin is smelted. The crushed cassiterite is heated and stirred with coke for about 15 hours. The coke provides enough carbon needed for removing oxygen from tin oxide.

The impurities that float to the top are then removed. The molten tin is poured into moulds and is left to cool down. The solidified tin is then refined to remove any impurities that may still be remaining.

Refining tin is another process altogether. To refine tin, it is heated to about 1200 degree Celsius in vacuum. When the tin melts, remaining impurities will boil away to leave behind tin that is 99.85 per cent pure. By using a process called electrolysis, tin can be refined further.

Though our ancestors believed that tin plague was caused by witchcraft, we now know that it is caused by a change in the structure of the metal. After scientific studies, metallurgists found that tin- and some other metals too – has different crystalline forms at different temperatures.

At normal temperatures, the crystals that make up the metal are stable. The metal exists in the form of white tin in normal temperatures. But, when the temperature drops below 13 degrees, the crystals take a new form; the internal stresses caused by the change in temperature causes the metal to disintegrate into a grey powder. After many experiments, scientists found out that this condition can be corrected with an ‘injection’ of a substance called bismuth.

When bismuth is added to tin, it stabilizes the metal so that the tin crystals will no longer become unstable and disintegrate when exposed to severe cold. Tin can also be stabilized using antimony, another element.

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