Category Science

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’.