Category Science

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.