Lithium

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The name lithium derives from the Greek word lithos which means "a stone." It is a very light, soft, silver-white metal. It is so soft that you can cut it with a knife. And it is the lightest metal, in fact, the lightest of all solids. It is five times as light as aluminium – a cubic foot of aluminium weighs 169 pounds, while a cubic foot of lithium weighs only 33 pounds. Lithium is even lighter than cork and will float on water and oil. It is so light, indeed, that two men might easily lift an aeroplane made from lithium. But you can make neither an aeroplane nor even a spoon from lithium. Why? Because lithium readily combines with air and water as it is so unstable. And do you know what might happen if you stirred hot tea with a spoon made from lithium? The spoon would simply disap­pear.

But lithium has come into use quite recently. For many years after its discovery in 1817 lithium was a useless curiosi­ty. In the early 1880's, Thomas Edison began using it in electric batteries. And it is still used for this purpose in two-way signal systems and in the television picture tube. Now it is also used in the making of vitamin A and other drugs.

Li­thium has other interesting uses: in the manufacture of soap and lubricating oils. In fact, a lubricating oil that contains lithium may be very successfully used both in the tropics and in the Arctic regions. In 1951 the United States of America used 50% of its lithium for lubricating oils.

Lithium is still costly, but it is generally used in small amounts. Though it is still high-priced it is cheaper and more plentiful than uranium. And weight for weight, lithium could give three times more energy than uranium.

Lithium has been used for purifying air in submarines, de-icing aeroplanes and for making signal flares since World War II.

When the war was over resourceful scientists found other uses for this wonder-metal. They soon discovered that lithium was good for purifying copper and bronze castings, that it was valuable in steel-making and could be used in air-condition­ing units.

Most of it comes from the United States, Canada and South Africa. The metal is widely distributed but in small deposits. Mining and refining costs are high. That's why lithium is still high-priced.

14. Choose the correct form in the brackets:

1. Recently vanadium (has been tried/ has tried) in treating infected wounds. 2. Lithium (have come/ has come) into use quite recently 3. Lithium (has/had/have) many other interesting uses. 4. Cobalt (has found /has been found) in marine organisms. 5. You have certainly (heard/certainly have been heard) of such metals as hafnium, cerium, cesium. 6. It (have been stated /has been stated) that small addition of vanadium strengthens the alloys. 7. Vanadium (has always been/always has) of great valuein making high-quality steel-alloys.

15. Put in the right tense: Past Simple, Present Perfect or Past Perfect.

1. Vanadium (was discovered/ has been discovered) in 1801, but many years (have passed/had passed) before metallurgists realized its great value.

2. As you may (have heard/ heard) the most common use of cesium is the pho­toelectric cell as the "electric eye". It was discovered so late because it (was 15. never found/ has never been found) pure.

3. The Japanese (had used/used) molybdenum in steel-making long before the European (learnt/had learnt) about its wonderful properties.

4. They named the metal hafnium, which is the Latin for Copenhagen, the place where it (was discovered/had been discovered). (Has/did) it found any other important uses since then?

5. In 1815 the famous Swed­ish chemist Berzelius thought he (has obtained/had obtained) a new element from gadolinite, a mineral. He named it thorium, in honour of Thor, the Scandinavian god of thunder.

16. Match the metals in A with the group they belong to in B. Make sentences using the phrases to class(with), to belong to, to be defined as, to be considered.

Model: Selenium is defined as semiconductor.

A	B
1. rhodium, iridium	a. refractory
2. gadolinium, ytterbium	b. rare-earth
3. thorium, californium	c. platinum
4. molybdenum, niobium, zirconium	d. radioactive
5. beryllium, cesium	e. heavy
6. lead, chromium	f. light

17. Consult a dictionary to make sure you read and understand the following words correctly:

proceeding, alumina, bauxite, abrasive, emery powder, corundum, precious, precision, jewel, ruby, sapphire, furnace, commercial.

Дата добавления: 2014-11-07