The following list is just some of the uses of Magnesium:
- used in flares and pyrotechnics, including incendiary bombs. It was used in flash photography,
- it is lighter than aluminium, and is used in alloys used for aircraft, car engine casings, and missile construction
- it is used a reducing agent for the production of uranium and other metals from their salts
- the hydroxide (milk of magnesia), chloride, sulphate (Epsom salts), and the citrate are used in medicine
- magnesium oxide is refractory and used as bricks and liners in furnaces
- used to make organomagnesium compounds (Grignard reagents), useful in organic synthesis
- used in computers for radio-frequency shielding
Aluminium (Al)
Aluminium is silvery in colour and a solid at room temperature. It is conductive to both heat and electricity. It has a melting point of 933.57 K and a boiling point of 2740 K.
Aluminium is an abundant element in the earth's crust, but it is not found free in nature. The Bayer process is used to refine aluminium from bauxite, an aluminium ore.
Aluminium is easily formed, machined, and cast. Pure aluminium is soft and lacks strength, but alloys with small amounts of copper, magnesium, silicon, manganese, and other elements have very useful properties.
Aluminium is mined in huge scales as bauxite (typically Al2O3.2H2O). Bauxite contains Fe2O3, SiO2, and other impurities. In order to isolate pure aluminium, these impurities must be removed from the bauxite. This is done by the Bayer process. This involves treatment with sodium hydroxide (NaOH) solution, which results in a solution of sodium aluminate and sodium silicate. The iron remains behind as a solid. When CO2 is blown through the resulting solution, the sodium silicate stays in solution while the aluminium is precipitated out as aluminium hydroxide. The hydroxide can be filtered off, washed, and heated to form pure alumina, Al2O3.
The next stage is formation of pure aluminium. This is obtained from the pure Al2O3 by an electrolytic method. Electrolysis is necessary as aluminium is so electropositive. It seems these days that electrolysis of the hot oxide in a carbon lined steel cell acting as the cathode with carbon anodes is most common.
The following list is some of the uses of Aluminium:
- cans and foils
- kitchen utensils
- outside building decoration
- industrial applications where a strong, light, easily constructed material is needed
- although its electrical conductivity is only about 60% that of copper per area of cross section, it is used in electrical transmission lines because of its lightness and price
- alloys are of vital importance in the construction of modern aircraft and rockets
- aluminium, evaporated in a vacuum, forms a highly reflective coating for both visible light and radiant heat. These coatings soon form a thin layer of the protective oxide and do not deteriorate as do silver coatings. These coatings are used for telescope mirrors, decorative paper, packages, toys, and in many other uses
- the oxide, alumina, occurs naturally as ruby, sapphire, corundum, and emery, and is used in glass making and refractories. Synthetic ruby and sapphire are used in the construction of lasers
Silicon (Si)
Silicon is dark grey with a bluish tinge in colour and a solid at room temperature. It is conductive to both heat and temperature. It has a melting point of 1683.2 K and a boiling point of 3553 K.
Silicon makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen. It is found largely as silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal. Silicon is found also in minerals such as asbestos, feldspar, clay and mica. Silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites. Silicon is not found in nature independent of anything else.
Silicon is important in plant and animal life. Diatoms in both fresh and salt water extract silica from the water to use as a component of their cell walls. Silicon is an important ingredient in steel. Silicon carbide is one of the most important abrasives.
Hydrolysis and condensation of substituted chlorosilanes can be used to produce a very great number of polymeric products, or silicones. These range from liquids to hard, glasslike solids with many useful properties.
The following list is some of the uses of Silicon:
- doped with boron, gallium, phosphorus, or arsenic, etc. to produce silicon for use in transistors, solar cells, rectifiers, and other electronic solid-state devices
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silicones are important products of silicon. They are prepared by hydrolysing a silicon organic chloride, such as Me2SiCl2
- silica, as sand, is a principal ingredient of glass, a material with excellent mechanical, optical, thermal, and electrical properties
- computer chips
- lubricants
- used to make concrete and bricks
Phosphorus (P)
Phoshorus is either colourless, red or silvery white. It is a solid at room temperature. It is conductive to heat and electricity. Its melting point is 317.3 K and its boiling point is 553.7 K.
Originally, phosphorus was extracted from urine. However there is plenty of phosphorus in phosphate ores and those ores represent the usual source for commercially produced phosphorus. There is normally no need to make phosphorus in the laboratory as it is readily available commercially.
The following list is some of the uses of Phosphorus:
- used in the manufacture of safety matches, pyrotechnics, incendiary shells, smoke bombs, tracer bullets, etc.
- fertilisers
- phosphates are used in the production of special glasses, such as those used for sodium lamps
- bone-ash, calcium phosphate, is used to produce fine chinaware and to produce monocalcium phosphate used in baking powder
- important in the production of steels, phosphor bronze, and many other products
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Na3PO4 is important as a cleaning agent, as a water softener, and for preventing boiler scale and corrosion of pipes and boiler tubes
- Pesticides
Sulphur (S)
Sulphur is a pale yellow, odourless, brittle solid, which is insoluble in water but soluble in carbon disulphide. It is a solid at room temperature. Its melting point is 386 K and its boiling point is 717.9 K.
Sulphur is found in meteorites, volcanoes, hot springs, and as galena, gypsum, Epsom salts, and barite. It is recovered commercially from "salt domes" along the Gulf Coast of the USA. Jupiter's moon Io owes its colours to various forms of sulphur. A dark area near the crater Aristarchus on the moon may be a sulphur deposit. It is found as the native element in nature and extracted by the Frasch process. This is an interesting process since it means that sulphur can be extracted from underground without mining it. In the Frasch process underground deposits of sulphur are forced to the surface using superheated water and steam (160°C, 16 atmospheres, to melt the sulphur) and compressed air (25 atmospheres). This gives molten sulphur which is allowed to cool in large basins. Purity can reach 99.5%.
The following is a list of some of the uses of Sulphur:
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Most of the sulphur produced is used to produce sulphuric acid, H2SO4, the most important manufactured chemical in the world. Sulphuric acid has many uses, including for the synthesis of fertilisers and polyamides. It is used in batteries ("battery acid").
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Sulphur is a component of black gunpowder (a mixture of potassium nitrate, KNO3, carbon, and sulphur). It is used in the vulcanisation of natural rubber, as a fungicide, and as a fumigant.
- Sulphur compounds are used in the bleaching of dried fruits and for paper products.
Chlorine (Cl)
Chlorine is a gas at room temperature taking on a greenish/yellow colour. Chlorine has a melting point of 172.22 K and a boiling point of 239.2 K. It is not conductive to heat or electricity.
Chlorine is never found in nature as the free gas. It is found mainly as rock salt (common salt, halite, NaCl), carnallite (KMgCl3.6H2O), and sylvite (KCl).
The following is some of the uses of Chlorine:
- production of safe drinking water the world over. Even the smallest water supplies are now usually chlorinated
- extensively used in the production of paper products, dye stuffs, textiles, petroleum products, medicines, antiseptics, insecticides, foodstuffs, solvents, paints, plastics, and many other consumer products
- most chlorine is used in the manufacture of chlorinated cleaning compounds, pulp bleaching, disinfectants, and textile processing
- manufacture of chlorates, chloroform, carbon tetrachloride
- used for the extraction of bromine
- PVC pipe used to provide safe drinking water
Argon (Ar)
Argon is a gas at room temperature. Argon is colourless; it is also inert. Argon has a melting point of 84 K and a boiling point of 87.3 K. It is not conductive to heat or electricity.
Argon is present to a small extent in the atmosphere and is obtained as a by-product from the liquefaction and separation of air. This would not normally be carried out in the laboratory and argon is available commercially in cylinders at high pressure.
The following is a list of some of the uses of Argon:
- used in electric light bulbs and in fluorescent tubes at a pressure of about 3 mm, photo tubes, glow tubes, etc.
- used as an inert gas shield for arc welding and cutting
- blanket for the production of titanium and other reactive elements
- protective atmosphere for growing silicon and germanium crystals ,lasers, light bulbs electric light bulbs and fluorescent tubes, photo tubes, glow tubes, welding, cuttin Argon is present in the atmosphere which contains nearly 1% argon gas
- Argon gas is not toxic but in principle it could asphyxiate through denying the body access to oxygen
Bibliography
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J.E. Huheey, E.A. Keiter, and R.L. Keiter in Inorganic Chemistry : Principles of Structure and Reactivity, 4th edition, HarperCollins, New York, USA, 1993
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N.N. Greenwood and A. Earnshaw in Chemistry of the Elements, 2nd edition, Butterworth, UK, 1997.
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F.A. Cotton, G. Wilkinson, C.A. Murillo, and M. Bochmann, in Advanced Inorganic Chemistry, John Wiley & Sons, 1999.
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D.R. Lide, (ed.) in Chemical Rubber Company handbook of chemistry and physics, CRC Press, Boca Raton, Florida, USA, 77th edition, 1996.
