Category Chemistry

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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