Category Metal & Non-Metals

A group of six metals – ruthenium, rhodium, palladium, osmium, iridium, and platinum-are known as the platinum group of metals or PGM. The group is called by this name because platinum is found more than the others though all of them are very rare.

The platinum groups of metals have physical, chemical and anatomical similarities. They are dense, stable and are often recycled to have longer lives. The group has a variety of highly specialized uses.

Platinum is a silvery white metal that is more expensive than gold. It is used to make jewellery. Platinum and palladium are often used as catalysts. Iridium and rhodium are harder and have a lot of alloying applications. There are very few minerals containing the platinum group of metals, and they are found mainly in South Africa and Russia.

No one knew of the dangers radium posed when it was produced for the first time. Radium had an aura of mystery which attracted people. Moreover, people were fascinated by how it glowed when mixed with phosphor. No wonder, industries sprang up to manufacture hundreds of consumer products containing radium.

The health hazard caused by this fascinating new element was identified only later. The harmful effects of radium such as skin burns and hair loss were observed among early experimenters. Many of them died as a result of their work.

The widespread use of radium was later halted for health and safety reasons. But, its wide use in luminescent paints continued through World War II. The soft glow of radium’s luminescence made aircraft dials, gauges and other instruments visible to their operators at night.

Radium was also an early radiation source for cancer treatment. Small radioactive seeds were implanted in tumours to kill cancerous cells. Safer and more effective radiation sources are used today.

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The discovery of radium is one of the most interesting stories in science. The story begins with the research of the French physicist Antoine-Henri Becquerel of the ore called pitchblende containing the element uranium. Becquerel found that pitchblende gives off radiation.

Becquerel’s discovery caused great excitement among scientists. Many physicists stopped their own research and began to study this novelty. A scientist couple Marie and Pierre Curie were especially interested in pitchblende.

Eventually, they isolated a new element that gave off more intense radiation than pitchblende itself. The Curies named this new element polonium. That was not the end. They believed that there would be at least one other element in the pitchblende.

The couple continued with their studies and in 1898, they isolated a second new element- radium. Radium gave away intense radiations and it took the Curies another four years to prepare one gram of the element. To do so, they had to sift through more than seven metric tons of pitchblende!

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Strontium is a silvery metal that rapidly turns yellowish in air. It is found as a free metal in nature and is not dangerous. This is because the naturally occurring strontium is not radioactive. But strontium has some isotopes that are highly unstable and potentially dangerous. Strontium-90 is one such isotope of strontium.

Strontium-90 is produced as a result of a nuclear reaction. It became famous in the 1960s when it was produced as the result of an atomic bomb testing. In fact, when a nuclear explosion takes place, the tens of millions of tons of earth and rock that are thrown skywards contain strontium-90.

Strontium-90 contaminates air, water, soil and vegetation; severe radiations produced in the process can sicken both animals and humans and can even result in deaths.

Strontium-90 affects human bone tissues, marrow and blood. It can cause leukaemia and bone cancer too.

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Let us now talk about something that was common in ancient India. Very often, mysterious red lights would flare up in temples to the awe and terror of worshippers, who believed it to be a divine light.

Actually, it was the handiwork of priests who would quietly set fire to small balls of a mixture that contained strontium salts. Strontium catches flame spontaneously in air and strontium salts impart a beautiful crimson colour to flames. For this reason, strontium is used in fireworks as well.

Strontium is a soft silvery metal that is found chiefly as celestite and strontianite. It was in 1808 that Sir Humphry Davy isolated strontium. But much before that, our ancestors knew about this metal and had used it in quite a cunning manner.

You might have heard stories about ships that sent red flares as a symbol of trouble. Just like the ones used in ancient Indian temples, these ships too used strontium salts. It would not be wrong to say that strontium has saved many lives.

Let us now take a look at how glass is made. Glass is made by melting a special type of sand called silica sand. The sand melts at 1700 degree Celsius; it must be melted and cooled down quickly. This process requires a huge amount of energy and will produce a lot of heat.

To make things easier, sodium carbonate is added. Sodium carbonate breaks down in the heat to form sodium oxide, and reduces the melting temperature. This does not completely solve the problem.

The glass made after adding sodium carbonate would dissolve in water. This is where calcium carbonate comes into the scene. When calcium carbonate is added to glass, it forms calcium oxide in the glass. About 90 per cent of glass in the world is made in this fashion.

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You cannot lead an active life without calcium. Be it walking, running, playing games, lifting things or even sitting straight, you cannot do any of these if not for calcium.

Every cell in our body needs calcium. Calcium helps our muscles work and send nerve impulses. It helps your body to heal cuts, scrapes and other injuries. Our bones store calcium that is necessary for our blood and cells; our bones are built and strengthened with calcium right from the day we are born.

If our diet does not include enough calcium, our body will consume the calcium that is stored in the bones. This will eventually make our bones weaker. So, it is important to have calcium rich foods like curd and milk.

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Chalk is a white crumbly rock made of microscopic shells and is rich in calcium carbonate. Chalk is softer than limestone and is used to make a substance called putty. Putty is used to fill holes in woodwork, give a smooth finishing to the walls of buildings and seal glass into windows. Chalk is also ground into a powder called whiting, which is used in crayons, rubber paints and cosmetics.

Limestone often contains the fossils of dead animals and plants that were trapped in between the layers of sediment. Limestone is hard enough to be qualified as a building material; it is used to construct buildings, walls and paving stones. Sometimes, limestone contains phosphates. This is used to make fertilizers.

Marble is formed when chalk or limestone is buried deep underground. The pressure and heat changes the limestone or chalk into marble. It is hard, yet shiny and beautiful. Therefore, marble is used in flooring. Many sculptures and buildings around the world are made of marble. The famous Taj Mahal is built entirely of marble.

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Calcium makes about 3.6 per cent of the Earth’s crust. But it is rarely found as a free metal. Calcium is abundant on the surface of the Earth and is mostly found as chalk, limestone, or marble.

Let us now look at how these calcium deposits are formed. The shells of living things in the ocean are made of calcium carbonate. When they die, they sink to the bottom of the ocean. Over the years, these form layers of sediments. As the layers build up, their weight squeezes the water trapped between and they stick together. Over thousands of years, the shells are transformed into sedimentary rocks called chalk, limestone and marble.

It was Sir Humphry Davy who isolated calcium for the first time in 1808.

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To maintain good health, the human body needs a lot of minerals like iron, calcium and sodium. We have already discussed how our blood is enriched by iron. But, very few people are aware of the enormous role magnesium plays in our bodies.

After oxygen, water and food, magnesium may be the most important element needed by our bodies. In fact, it is by far the most important mineral in the body.

Magnesium is necessary for over 300 different biochemical reactions that help the functioning of the human body. Magnesium is necessary for the growth and strength of bones and teeth. It plays an important role in the synthesis of protein and is responsible for fighting infections. Magnesium is vital for muscle contraction and the functioning of nerves.

Needless to say, we need to eat a lot of food that is rich in magnesium like nuts, whole grains, dark green vegetables, seafood, and cocoa.

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Iron and steel corrode after being exposed to oxygen or water. Corrosion is a huge trouble for ships, pipelines and oil rigs.

To prevent the troubles caused by rusting and protect the iron, another metal is used. Magnesium and zinc are often used for this purpose.

Magnesium is either attached with a cable or bolted to an object made of iron or steel. This method is known as sacrificial protection. As long as magnesium stays in contact with the steel or iron, the rust will form on the magnesium bar, since it reacts more strongly with oxygen and water than either of the other two metals. When the rust attacks the magnesium bar, it will be eaten away.

One magnesium bar must be replaced with another to protect iron or steel. Since magnesium is willingly allowed to be destroyed for the protection of iron or steel, this method is known as sacrificial protection.

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Magnesium was not discovered until the 19th century. But much before that, humans had been using compounds of magnesium. Isolating magnesium is a tough task. This is because the compounds of magnesium are highly stable and cannot be broken down easily.

Careful studies of magnesium and its compounds began in the mid 1700’s. Some of the earliest studies on magnesium and its compounds were carried out by Joseph Black, a Scottish physician and chemist.

He conducted various experiments on compounds of magnesium and published his studies in an article. Black’s article became famous in the scientific circles and he is sometimes given credit for ‘discovering’ magnesium.

Though Black’s experiments were famous, it was Sir Humphry Davy who first isolated magnesium. Davy passed an electric current through melted magnesium oxide. The current caused the compound to break apart, forming the impure magnesium metal and oxygen gas. But this was a strenuous task, requiring a large battery with 200 pairs of metal discs to isolate the metal!

In 1798, a French chemist, Louis-Nicolas Vauquelin discovered a brittle, steel-gray metal. It was found as a component of coal, oil, certain rock minerals, volcanic dust, and soil. This metal was named beryllium.

Beryllium is used to make an alloy – beryllium copper- which has a wide variety of uses. Beryllium copper is used to make springs, electrical contacts, spot-welding electrodes, and non-sparking tools.

This alloy absorbs a lot of heat energy without becoming as hot as other metals. It is used in high-speed aircraft, missiles, spacecraft, and communication satellites for the same reason. It is also used to make windshield frames, brake discs, support beams, and other structural components of the space shuttle.

Though ordinary light cannot pass through beryllium, X-rays seep through it. So, it is used in the windows of X-Ray machines and radiation detectors. It is used to make computer parts and instruments where lightness, stiffness, and stability are required and even in nuclear reactors.

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The method of spectroscopy was instrumental in the discovery of some elements. Spectroscopy is the process of analyzing light produced when an element is heated. Each element produces a different light when heated.

The spectrum of an element consists of a series of coloured lines. In many cases, the amount of an element present in a sample is too small. But, the element is much easier to detect by spectroscopy.

Caesium was discovered using spectroscopy by two German scientists, Robert Bunsen and Gustav Kirchhoff. It happened in 1859. Bunsen and Kirchhoff discovered caesium while they were busy studying a sample of mineral water taken from a spring.

At first, they identified the spectral lines for sodium, potassium, lithium, calcium, and strontium; these elements were well-known at that time. After removing these elements from the sample, they could still see two blue lines in the spectrum.

This was due to the presence of caesium. It was Bunsen who suggested calling the element caesium; it is derived from the Latin word for ‘sky blue’.

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Francium is one of the most radioactive elements in nature. Apart from being one of the least stable elements, it is also the second rarest naturally occurring element on Earth.

Marguerite Perey discovered francium in 1939. She chose to name the metal after France, the nation of its discovery. Francium is formed when uranium and thorium ores decay. It is usually made from radium in nuclear reactors.

Numerous experiments and calculations have been carried out since francium was discovered to study its basic physical and chemical properties. The half-life of this element is around 22 minutes.

Due to its high reactivity, francium is not used commercially. However, from experiments conducted on rats, scientists have proved that francium is a promising aid in the early diagnosis of cancer. This is because francium accumulates in cancerous tissues.

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Like sodium, potassium is another metal famous for its reactivity; it is so active that it never occurs freely in nature, but only as compounds. This was why our ancestors did not know about the existence of this metal. Potassium was not known to the world until the 19th century.

The term potassium comes from potash. Early humans were familiar with potash, a compound of potassium that was formed when wood burns. Wood ash was washed with water to dissolve the potash. It was then recovered by evaporating the water. By the late I700’s, chemists were reasonably sure that potash contained elements they had never seen. They tried to think of ways to break potash down into its elements. However, it was the English chemist Sir Humphry Davy who finally found a way to make potassium from potash.

In 1807, Humphry Davy prepared potassium in its pure form for the first time in the world. He was using his newly invented method of isolating elements, known as electrolysis. In electrolysis, electric current is passed through a molten or melted compound which breaks the compound into its elements.

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The reactivity of rubidium might surprise you. In fact, rubidium is one of the most reactive of all the metals in the world. It catches fire when exposed to oxygen in the air, and burns up with a bright pinkish purple flame to become a yellow powder called rubidium superoxide.

If you try to put out the fire with water, it will only make matters worse. Want to know why? Rubidium reacts vigorously with water as well! When exposed to water, it produces hydrogen gas, which catches fire and burns.

By now, you would have understood why it is difficult to store rubidium. Most of the containers are not suitable for preserving or storing rubidium. If you place it in an ordinary glass container, the rubidium will destroy the glass at high temperatures. The only solution is to store it in special glass tubes in which a vacuum is maintained, or in flasks of kerosene or paraffin oil.

The name ‘rubidium’ comes from the term ‘rubidus’, which was a word once used to refer to the deepest red.

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Sodium is notorious for its reactivity; it reacts quickly with air and water. Therefore, sodium is rarely used by itself though it is an important industrial metal. Let us now take a look at some of the uses of sodium.

Sodium is used for manufacturing many organic compounds and also to improve the structure of certain alloys. It is an indispensable element in the manufacture of soap, paper, textiles, glass and petroleum. We all consume sodium on a daily basis. There is a great variety in the compounds of sodium. Sodium silicates are used as fillers for salt, and in detergents. Sodium tetra borate is known as borax. Sodium hydroxide is used in the manufacture of paper, soap, rubber and rayon. It is also used for refining oil. Sodium fluoride is used in antibiotics, rat poison, and in ceramics. Sodium hydroxide gets grease out of the drains; it is also used to make liquid soap.

We consume sodium on a daily basis. The table salt that we use in our food is sodium chloride, a compound of sodium. Baking soda that we use to make baked goods is actually sodium bicarbonate, another compound of sodium.

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You might have heard of lithium batteries that are used in laptops and mobile phones. Lithium batteries replaced the lead-cadmium batteries as they are lightweight and not as toxic as their counterparts. The devices that use lithium batteries range from watches to spacecraft.

Lithium-6 is an isotope of lithium which is used as a fuel for nuclear reactors. Lithium is preferred as a nuclear fuel, because it is cheaper and more available. In addition to being a nuclear fuel, it is also used in rockets and spaceships. If lithium is added to water it produces highly flammable hydrogen.

Ceramics, enamels, glass, lubricants, rubber products and certain dyes also use lithium. It is used in some medicines as well. Lithium is used as an air purifier in submarines, aircraft and even air conditioners.

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Let us now look at the varied uses of mercury. Mercury is used as an electrode in the production of chlorine and sodium hydroxide. It is also used in certain electric batteries.

It is used in barometers and manometers. It is also used extensively in thermometers. Mercury is important as a liquid contact material for electric switches. It was also used in mercury-vapour lamps that were used for street lighting.

Mercury forms a special type of alloy with some metals like silver, and tin. These alloys are used in dentistry for filling teeth. Several compounds of mercury are used as disinfectants.

They are also used to make substances including insecticides and rat poison. Mercuric oxide is used in skin ointments, though of course people handle it with a great deal of care now, because of the danger of mercury poisoning.

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Mercury is not a common metal. It is rarely found on Earth’s crust. In fact, it forms only 0.00005 per cent of the crust. However, there are more than 20 minerals that contain mercury. It is found in cinnabar, cordierite, livingstonite and some other minerals, with cinnabar being the most common ore.

Mercury ores usually occur at hot springs or other volcanic regions. Globally, mercury is most commonly produced in Spain; the Almaden mine there is known for its high quality mercury. It is also obtained from the United States and Italy.

Mercury is named after the planet Mercury, which in turn, is named after the Roman God Mercurius, the God of trade, profit and commerce. Mercury is sometimes called quicksilver because of its silver colour. In fact, its chemical symbol ‘Hg’ comes from the Greek word ‘hydrargyrum’ which means ‘water silver’.

You might already know that alchemy flourished in the Middle Ages when people began going crazy over gold. They also believed that mercury could be converted into gold if they found the philosopher’s stone.

Alchemists would heat mercury with nitric acid to prepare mercuric oxide. The reaction produced a thick red vapour, which hovered over the surface of the solution. The mercuric oxide that was formed would fall to the bottom of the liquid in the form of bright red crystals.

Many of the alchemists used these crystals to fool people about the supposed powers of mercury including the power to grant eternal life. Some alchemists also used mercury to demonstrate that gold could be made artificially.

There are evidences that suggest that mercury was known to humans before at least a thousand years. Mercury has been found in Egyptian tombs that date back to 1500 BC. The ancient Chinese and Indians were familiar with the liquid metal. In fact, our ancestors thought of mercury as the first matter from which all metals were formed.

In countries like India, China and Tibet, it was believed that mercury could prolong life, heal fractures, and maintain good health. While the ancient Greeks used mercury in ointments, the Romans used it to make cosmetics.

Our ancestors believed that varying the quality and quantity of sulphur contained within the mercury could produce different metals. They even tried to transform mercury into gold. Needles to say, they were not successful!

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As already mentioned, mercury was widely used to make ointments, cosmetics and even dental fillings. But studies have revealed that the compounds and vapours of mercury are potentially hazardous as it can cause poisoning.

In fact, mercury poisoning is something to be feared as it does not affect just one part, but each and every system of the human body. It can cause other diseases as well.

Health problems caused by mercury depend on how much of it has entered your body, how it entered your body, how long you have been exposed to it, and how your body responds to mercury. There are many possible ways to get poisoned by mercury.

Some cosmetics can be harmful to us as it contains compounds of mercury. The people working in the paint industry are at risk as paint uses some compounds of mercury. Eating fish that have been exposed to mercury in the environment is also very dangerous.

In 1956, thousands of fishermen and their families in the southern Japanese city of Minamata fell ill because they ate fish that had been contaminated with mercury.

We have discussed the harmful effects of lead at length now. But why was lead widely used despite its hazardous impact? Undoubtedly, it was because lead was a useful metal. Let us now look at some of the usages of lead.

In the olden days, lead was used as a building material. It was used as a pigment for glazing ceramics. Water pipes were coated with lead. Today, the most prominent use of lead is to build lead-acid storage batteries. The electrical systems of vehicles, ships, and aircraft depend on such batteries for startup, and in some cases, batteries provide the actual motive power.

Have you heard of sound-proof rooms? Lead is used for soundproofing office buildings, schools, and hotels. It is widely used in hospitals for protection against X-ray and gamma radiation. Lead is also employed as a shield against harmful nuclear radiation.

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Earlier, lead was mixed in petrol for better performance. Lead was useful in helping the car engines better. If the petrol in the car burns too quickly, the engine starts rattling. Adding lead to petrol minimized wear and tear. But it created more problems than the benefits it offered.

Lead was poisonous and burning leaded petrol was a suicidal idea. It also increased pollution considerably. Studies conducted in different parts of the world proved that unleaded petrol caused much lesser pollution than leaded petrol. So, many countries have banned the use of petrol with lead added to it, and now only unleaded petrol is used.

Different additives have now replaced the lead compounds. The most popular additives include aromatic hydrocarbons, ethers and alcohol. However, fuel containing leads continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines in some parts of the world.

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The usage of lead has a history of more than a thousand years. Humans have mastered the technique of extracting lead from its ores for more than a thousand years. Lead is hardly found as a free metal in nature.

The main ore of lead is lead sulphide, which is also known as Galena. Galena is crushed to a fine powder, and then mixed with water and some other chemicals. As a result of this, the lead sulphide will float to the top in the form of froth, and the waste rock will sink to the bottom. The froth is then dried and mixed with limestone to remove the sulphur from the lead sulphide. This leaves behind lead oxide.

The lead oxide is further crushed and heated in order to obtain molten lead after removing the oxygen molecules. It is purified further to make it ready for sale.

There is no doubt about the importance of lead in the lives of ancient humans. It was used to make pipes, vessels and a lot of other things. However, lead was also looked at with fear; this metal was vital in many torture mechanisms that were used to punish criminals.

In the Middle Ages, lead was used as an instrument of torture. Hot molten lead was poured into the ears of anyone suspected to be against the religious beliefs of the time. This was because lead melts easily. In Venice, prisoners were held in an attic with a lead roof that would make the cells unbearably hot in summer and unbearably cold in winter. Their screams of agony could be heard all day even outside the prison!

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To find one gram of silver, you need to drill through at least 20 tons of rock! Silver makes up only a tiny proportion of the Earth’s crust. Silver indeed is a rare metal.

Silver is found either as a free metal, or in combination with other elements. We can extract silver from silver ores; the most prominent silver ore is asanthite or argentite. Lead sulphate or Galena is another important source of silver. The principal sources of silver are the ores of copper, copper-nickel, lead, and lead-zinc obtained from Peru, Mexico, China, Australia, Chile, Poland and Kosovo. Peru and Mexico have been mining silver since 1546 and are still major world producers of this lustrous metal.

About 18,000 tons of silver are produced every year. But extracting silver is a tough process. A lot of it comes from the waste left behind after refining copper, lead or zinc. Although silver is relatively scarce, it is the most plentiful and least expensive of the precious 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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Tin plague can be really annoying and destructive. Captain Robert Scott’s was not the only expedition that was destroyed by tin plague. Tin plague had once devastated Napoleon’s plan. This phenomenon actually caused an army to lose a war.

In 1812, Napoleon invaded Russia and marched to Moscow. However, his attempt to capture the city of Moscow failed, and one of the reasons given was that his soldiers were disheartened and uncomfortable because they could not stand the cold.

Napoleon had brought a million greatcoats for his troops, but these coats all had tin buttons. You can now imagine what happened, right? In winter, the tin buttons just crumbled away leaving Napoleon’s soldiers shivering and in no mood to fight!

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We know of humans, animals and plants falling sick. But is it possible for a metal to fall sick? What is tin plague? Let us now find out the answers to these questions.

Just like you become weak when falling sick, tin grows weak in chilly weather. In very cold weather, ordinary white tin turns to a powdery grey substance that disappears after some time. This phenomenon is known as tin plague. Tragically enough, tin plague had caused the death of many members of an expedition to the South Pole that was led by Captain Robert Scott. They carried kerosene in cans soldered with tin. Kerosene was important for the expedition as it could be used to start fires in the freezing climate.

In the extreme cold weather, tin turned to a powdery dust. As a result, the cans sprung leaks and all the kerosene just dribbled away. It was a horrifying tragedy, for it meant that the members of the expedition had no kerosene to start fires to cook and warm themselves; they died of hunger and cold.

If you coat some paper with silver chloride and expose it to light, you will find out that the silver chloride will turn black where the light falls on it. If you cover it with something like a leaf, the part covered by the leaf will remain white.

If compounds of silver like silver bromide, silver chloride or silver iodide are exposed to light, they break down to form tiny particles of silver that look black. An English scientist called William Talbot used this reaction to make photographs.

To develop a photograph, a thin layer of silver bromide is deposited on a sheet of photographic paper, and exposed to light. This produces a negative image from which the photograph is printed. Digital photography succeeded this technique which is no more in use now.

Silver is one of the most romantic and sought after precious metals. In many cultures, silver is an auspicious gift. Silver’s superior properties make it a highly desirable industrial component. Silver has both industrial and decorative uses.

Since a long time, silver has been used to make exquisite jewellery and elegant tableware. The mirror in which you see your face every day is coated with silver. In ancient times, wealthy people had mirrors and many other everyday objects made of pure silver.

Silver is a very good conductor of electricity, so it is widely used in industry, especially in electronics where it is used for printed circuit boards and electrical contacts. It is also used as a catalyst and is important in the production of solar energy. Another fascinating aspect of silver is the use of silver iodide in fighting tropical storms.

Silver played an important role in the history of Argentina, a South American country at the bottom of the continent. The name Argentina comes from the Latin ‘argentum’, meaning silver. ‘Argentina’ therefore means the ‘land of silver’. But how did this country get its name? Let us take a look.

In the early 1500s, Spanish conquistadors had heard tales about a land ruled by a White King that was rich in silver. They set on a voyage up a river in search of this wealthy kingdom. They discovered a group of native Indians, who presented them with so many silver objects that the river was named ‘Rio de la Plata’ or Silver River. In time, the country itself was called La Plata which means ‘silver’ in Spanish. When the rule of Spain ended, the name was changed to Argentina, from the Latin word ‘argentum.’

In olden days, silver was used to make coins in many kingdoms. The practice of using silver coins slowly gained popularity. But silver was a rare metal. Later it was found out that the cost of silver used for making these coins was a lot higher than the value of these coins. But, there was a solution to this problem-add another element to silver!

            Finally, after a lot of experiments, it was found out that copper could be mixed with silver to make coins that looked like silver, which was much cheaper than the older practice. Since then, copper-silver alloy is used to make silver coins.

Today, if a silver coin is actually made of pure silver, the metal would cost more than 20 times the value of the coin. However coins of pure silver are still available. People buy them as an investment.

We have heard many stories of people drinking from silver cups and eating from a silver platter. While we use a glass or steel tumbler to drink water, many of our ancestors used tumblers made of silver. More than a practice that showed off wealth, this had something to do with hygiene. Silver has excellent anti-bacterial properties. It kills harmful bacteria in water. In fact, a few millionths of one gram, is enough to purify a litre of water! Our smart forefathers knew this, and that is why they used to store water in silver vessels, and drink from silver cups.

Even today, some people drop a few silver coins in their drinking water to purify it. Though we are sure about the anti-bacterial properties of silver, it is always safer to boil water before drinking it as there are so many germs today.

In our society, gold is seen as a symbol of wealth. Most of the gold that we see around us is in the form of jewellery and other artefacts. But gold has more desirable qualities than its beauty which makes it a valuable metal in the industry.

The properties of gold make it vital for the manufacture of components used in a wide range of electronic products including computers, telephones, cellular phones, and home appliances. Gold is used for shielding satellites and spacecraft from solar radiation because it is an excellent reflector of heat.

Gold is a vital element in medical research; it is even used in the direct treatment of arthritis and some other diseases. Gold is also widely used in dentistry; though getting a gold tooth to replace a natural one is rather expensive!

In some Asian countries, gold is used in food and drink, from fruit jelly to coffee. Some sweets are covered with gold leaf.

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You might have seen jewellery advertisements talking about something called carats. But what are carats? A carat is the proportion of gold in an alloy. But why do we mix gold with other elements? Let us take a look.

Pure gold is very soft. It is not possible to make jewellery and other artefacts with pure gold as it is not hard enough. Gold in its pure form breaks easily. So, it is often mixed with copper, silver or other metals to make it easier to work with. Pure gold is always 24 carat. But, most of the jewellery that we wear is made of 22 carat gold. If there is a higher proportion of copper or silver, the gold may be 18, 14, or even 9 carat gold.

The cheapest jewellery will be made of 9 carat gold, and the most expensive, of 22 carat gold. The greater the amount of gold in the mixture, the more expensive it will be.

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Archimedes is famous for the Archimedes Principle, which states that when an object is immersed in a fluid, it will displace a volume of fluid equal to the volume of the portion of the object immersed. There is an interesting tale behind this principle.

Archimedes used this principle to prove that a jeweller was cheating the king. The king suspected that a solid gold crown he ordered was partly made of silver. To find out if it was true, Archimedes took two pieces of pure gold and pure silver of the weight of the crown. He then immersed the gold, the silver, and the crown – one after the other – in a container filled to the brim with water. He then measured the volume of water that overflowed with each material.

Archimedes found that the crown displaced more water than the gold, but less than the silver. This proved that the crown contained some metal other than gold or silver, and that the jeweller had stolen some of the gold given to him, and replaced it with a cheaper metal!

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Around 1500 tons of gold are produced around the world every year. Most of this gold comes from South Africa. Two methods are used to extract gold from the rocks where it is found. Gold can be extracted using mercury. The minerals containing gold are mixed with mercury. The gold will dissolve in the mercury to form an amalgam or alloy of mercury. The amalgam is then filtered and heated so that the mercury evaporates, leaving pure gold behind. In another popular method, the minerals containing gold are added to a sodium cyanide solution.

This solution reacts with the gold to form a new compound. The solution is then filtered to remove impurities. Later, zinc is added to the solution which reacts with the compound to produce pure gold.

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Gold played an important role in the life and culture of ancient Egypt. Ancient Egyptians considered gold divine and indestructible. It was associated with the brilliance of the sun and the sun god Ra was called ‘the mountain of gold’. Gold was widely used in ancient Egypt to make ornaments and other objects of value.

The pharaohs of ancient Egypt used gold lavishly in their tombs, on the floor, on the walls, and in the huge sarcophaguses or burial urns. It was their belief in the magic and spiritual power of gold that led the Egyptians to bury their dead adorned with golden amulets and jewels, making their tombs great treasure troves of gold.

No wonder, ancient Egypt was regarded as one of the richest countries in the world. In fact, Egypt was known as ‘the golden land’.

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The practice of alchemy flourished in ancient civilizations and later, it gained popularity in Europe in the 19th century. The alchemists, people who practiced alchemy, searched for means to transform ordinary metals like lead into gold.

Alchemy flourished in the Middle Ages. This was due to the increasing popularity of gold. Kings, queens and common people desired gold alike. Furnaces were lit in gloomy basements of stone castles and secret experiments were performed with some mysterious liquids. Many alchemists believed that the purity of mind, body and soul was essential to pursue alchemy. They also believed that alchemy could prolong life.

In the Middle Ages, it was believed that a substance called the ‘philosopher’s stone’ could turn other metals into gold. Needless to say, no one ever discovered such a stone, nor did the experiments of the alchemists meet with any success.

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We all are familiar with the stories where kings reward artisans, craftsmen and good subjects with gold coins.

Gold was used as currency in many kingdoms. But where was it used as currency for the first time? Lydia, an ancient kingdom in western Turkey is believed to be the pioneer of gold currency. Lydia was a fertile kingdom, but its greatest asset was the river Pactolus; it carried gold deposits.

Around 643 to 630 BC, the Lydians began producing the first coins. They were quite crude, and were made of electrum, a naturally occurring pale yellow mixture of gold and silver. By about 560 BC, the Lydians had learned to separate the gold from the silver following which, King Croesus issued the world’s first gold coins. Shortly afterwards, in 546 BC, King Croesus was captured by the Persians, who came to adopt gold as the main metal for their coins.

Soon, gold coins were being used in many other ancient countries. But the credit of introducing gold currency lies with the Lydians.

Iron was popular in ancient India. The extraction of iron in India dates back to the 4th century BC. Iron was used to make ornaments, weapons and buildings.

Indian smiths had developed many advanced techniques of processing iron that did not exist anywhere else in the world in those days. Expert craftsmen created many beautiful structures from iron which have lasted centuries without rusting.

In Delhi, there is a famous iron pillar that stands testimony to the high level of skill achieved by ancient Indian ironsmiths. In fact, it has withstood corrosion for the last 1,600 years! This pillar had sparked the interest of many material scientists across the world.

The iron beams in the Surya temple at Konarak in coastal Orissa, and the iron pillar at Mookambika temple are also examples of the skill of the ancient ironsmiths in treating iron so that it became rust- resistant.

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Gold secured a place in the hearts of early humans the moment the sparkling yellow grains were discovered for the first time. Humans have longed for gold ever since then. Men fought for it, women adored it.

We know the story of king Midas. According to Greek mythology, king Midas was granted the boon to turn anything that he touches into gold. He jumped with joy when the leaves and fruits that he touched turned into gold. However, he soon realized that the boon that he had asked for was in fact, a terrible curse.

He could not eat or drink, nor even wash his hands. Everything he touched turned into gold the moment he touched it. The boon was finally taken back after begging the gods for mercy.

The story of king Midas conveys the importance that was associated with gold. He asks nothing else but gold. Ancient kings and queens have always tried to amass as much gold as they could. This is why gold has been called the ‘king of metals’ and ‘the metal of kings’.

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Modern construction work will be reduced to almost nothing if not for iron and steel. Want to know why? Let us take a look.

If you have visited a construction site, you will see a lot of large girders. The framework of steel girders that you see in the buildings under construction is designed to bear the weight of the building. Without this framework, buildings made from just stone or brick would have to have very thick walls at the bottom. This would limit their height.

Iron plays important roles in other construction activities too. Cast-iron is used to make buildings and fences, while railway tracks are made of steel. Iron is also an ideal material for building bridges.

The first iron bridge was built in 1778, and in 1818 the first iron ship was launched. You all know about Paris’s famous Eiffel Tower. This 300 metres tall tower is built of latticed iron. The uses for iron and steel in construction are many, and continue to expand as the years go by.

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You might have seen reddish orange patches on iron at times. These patches are known as rust. Rust forms on iron because of oxidization, when the oxygen of the air burns the surface of the iron. It can be rubbed off in the form of fine powder just like ash.

Rusting damages the iron; it spoils the appearance of cars and buildings and the damage it causes costs a lot of money to be set right. However, rust is not that bad. It is actually beneficial to us in many ways.

Rust mixes with the soil, giving it a good brown or red colour. When powdered rust dissolves in water, it is taken up by plants and this eventually contributes to their green colour. Finally, through water and plants, we take iron into our bodies to give us the red colour of our blood.

Let us now look at how iron is converted into steel. Steelmaking is a tedious task. In most of the iron ores, iron is found in the form of iron oxides. We have already discussed how iron is extracted by heating it with coke using a, blast furnace.

The extracted iron might contain other metal impurities that are further removed or reduced by mixing it with scrap iron, blowing pure oxygen into the mixture, and adding calcium oxide later.

Slag will be formed as a reaction and it is removed. The iron extract after removing the slag is used to make steel. Other elements like manganese, chromium and nickel are added to the sourced iron to make steel.

The practice of steelmaking is centuries-old. Steelmaking flourished in the 19th century; nowadays, there are different techniques for steelmaking.

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Tools and weapons were essential for the survival of ancient humans. Since blacksmiths were the ones who made weapons and tools out of iron, they were revered. There is a beautiful old tale that illustrates how important blacksmiths were to a community.

Thousands of years ago, the wise king Solomon built a beautiful temple in Jerusalem. To celebrate the completion of the temple, he held a feast for his men. At the feast, he asked whose contribution to the creation of the temple was the greatest.

Everyone was in a hurry to make themselves sound important. The mason, the carpenter and the digger all claimed that theirs had been the most significant contribution. It was then that the king pointed out, that though their work was important; the greatest contribution was made by the blacksmith who made their tools, for without their tools they could not work, and without the blacksmith there would be no tools!

The early knowledge of iron comes from meteorites as we already mentioned. Early humans thought that these huge stones fell from heaven. Iron was the prominent element in the meteorites that fell on Earth. Many of them were made of up to 90 per cent iron. Therefore, iron was referred to and was described as ‘celestial stone’ in many ancient texts.

Hundreds of meteorites hit the surface of the earth every year. Some of these meteorites were really huge. One of the heaviest meteorites ever found is called the Hoba. This meteorite weighed about 60 tons.

In 1894, the polar explorer Robert Peary found a meteorite weighing 33 tons in Greenland. A gigantic iron meteorite hit the Arizona desert in prehistoric times leaving a crater that is 1200 metres in diameter and over 175 metres deep. The crater exists in Arizona even today.

Till about 1500 BC, iron was not a popular metal. Why was this so though iron was abundant on Earth? This was because of the difficulty in extracting iron, though the Hittites in West Asia did learn how to use it.

The Hittites kept the secret of making iron for about 400 years! They found out that iron weapons were better than bronze ones and that is why they decided not to tell anybody else how to make iron. The secret of making iron came to India with the Aryans. The Aryans invaded India around 1500 BC. People who lived in China learned how to make iron by around 700 or 600 BC. By about 300 AD, people in West Africa and East Africa too had learned the secrets of making iron.

Some people treasured iron more than gold as it was a rarity. Iron jewellery was worn by only the wealthiest people, and in ancient Rome, even wedding rings were made of iron! Though iron gradually became more easily available and cheaper, some tribes still considered it precious.

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The earth’s core is believed to consist largely of an iron-nickel alloy. In fact, iron makes up about 5 per cent of the Earth’s crust. Most of the iron in the Earth’s crust is combined with oxygen. Therefore, it is much more difficult to extract iron than other metals like copper.

Iron is extracted from iron ore in a huge steel column called a blast furnace. Coke, limestone and hot air are essential for the extraction of iron from its ore.

The blast furnace is heated by burning coke. When the coke burns, it produces carbon dioxide. The carbon dioxide reacts with more coke to produce a gas called carbon monoxide, which in turn reacts with the iron oxide in the iron ore to produce molten iron. The molten iron is then purified using limestone, and allowed to cool in moulds to produce cast iron.

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Some elements are essential for the normal growth and development of plant and animal life. Such elements are known as bioelements.

Plant life will be doomed if copper is not present on Earth. We all know that plants prepare food with the help of chlorophyll. Copper is essential for the production of chlorophyll; without it, the chlorophyll content of leaves would be reduced, turning them yellow. The plant would not be able to bear fruits and would eventually die.

Copper is necessary for animal life and human life too. Copper plays a crucial role in human growth. Copper is essential for bone strength, the maturation of red and white blood cells, cholesterol and glucose metabolism, the contraction of heart muscles, and brain development. Copper deficiency can lead to health problems such as anaemia, heart problems, bone abnormalities and complications in the functioning of the nervous and immune systems.

Your parents encourage you to eat iron-rich foods like spinach, lentils and dry fruits. Some of you might have been advised by doctors to take iron tablets for iron deficiency. But why do we need iron in our diet? Iron is an integral part of many proteins and enzymes that maintain good health in human beings and animals. So, all of us are iron boys and iron girls in this way!

Iron is one of the most abundant metals on Earth. This element is essential for plant and animal life. Plants need iron for the formation of chlorophyll, and for respiration. If a person’s blood does not have enough iron in it, he or she will become tired easily and suffer from frequent headaches. In fact, iron is vital for the production of haemoglobin, which gives blood its red hue.

Though it was known that iron has medicinal properties right from ancient times, the presence of iron in human blood was not discovered until the 19th century.

A chemical compound is obtained when two or more chemical elements are combined in definite proportions. The proportion of the elements is defined by weight. Some of the chemical compounds are useful to humankind.

Copper sulphate is one of the most important compounds of copper; it is used to refine copper. Copper sulphate has some agricultural uses as well. It is used as the base for many fungicides and also as an additive in animal feed. Copper oxide is used to make blue or green glazes in pottery. It is also used to colour artificial gems and glass.

Copper chloride is often used as a disinfectant. It is used for dyeing clothes and in textile printing too. Further it is used as a catalyst in many organic and inorganic reactions. While these compounds are useful to humans some of these compounds of copper can cause severe health problems as well.

Not only historical ages, but some revolutions too were named after metals. Here is the story of one such revolution.

In 1662, Russia was in a state of unrest. The people were exhausted after a lengthy war with Poland and Sweden. In addition to that, Russians were faced with frequent crop failures, as a result of which, heavy taxes were imposed by the Czar, or ruler of Russia. It was during this time that the Russian government decided to begin issuing copper money in large quantities instead of silver money, which was already in existence.

The replacement of silver coins was followed by a sharp rise in the prices of bread and other foodstuff. Needless to say, the people of Russia were infuriated by the changing social situations. They rioted in response to the changes on July 25 1662, but the Czar put down the riots with an iron hand. Hundreds of people were killed and thousands were either sent to prison or exiled to Siberia.

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Don’t be surprised to learn that copper has medicinal properties. In fact, copper is used in some of the traditional medicines across the world.

Many forms of copper and copper compounds, such as copper carbonate, copper silicate, copper oxide, copper sulphate and copper chloride were used throughout history for the treatment of disease. In ancient Egypt, copper was used to purify drinking water. Copper was also used to sterilize wounds, the treatment of headaches, trembling of the limbs, burns, and itching. The Greeks used copper for treating leg ulcers associated with varicose veins, while the Romans used it to purge stomach ache and treat ear and eye disorders.

Copper was chosen to make jewellery considering their health benefits. For many years, copper jewellery was worn as a remedy for various ailments, including arthritis. Many scholars across the world are still researching about the healing properties of copper.

Copper is one of the most used metals right from the beginning of civilizations. Copper had many qualities that were ideal for making tools, utensils and weapons.

This reddish brown metal is malleable and does not react with water or steam. It does not react with the oxygen in the air either, unless heated strongly. Copper is a good conductor of heat and electricity. That is why copper is used to make wires and utensils. Copper is used to make coins as well.

Copper is an indispensable metal in the electronic industry. In fact, almost all electrical devices rely on copper wiring because copper is inexpensive and highly conductive. Copper is mixed with other metals to make alloys with desirable properties.

The number of alloys made with copper is ever growing. Nowadays, copper is mixed with zinc, tin, aluminium, lead, silicon, manganese, cadmium and even chromium to make alloys.

The discovery of copper opened up new possibilities for humans. Copper exists in nature in the shape of nuggets. Gold and silver occur in the same shape, but they are very rare. Copper on the other hand is widely distributed and readily available.

Copper can easily be worked into different shapes. This was the reason why copper was preferred by the early humans. It was easy to make tools and weapons out of copper and they lasted longer than those made out of stone. They were much lighter than the stone toots as well. Moreover, copper tools could be sharpened again and again, so that they remained as good as new.

Early humans started with learning to extract copper from ores. Later their technology advanced; they began mixing copper with zinc to create an alloy called bronze, thus ushering a period known as the Bronze Age. 

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