Category Chemistry

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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