Aluminum is the most abundant metal and the third most abundant element in the earth's crust, after oxygen and silicon. It accounts for about 8% of the earth's total mass (Tar buck 103). Aluminum is a transition metal and is very chemically reactive; too reactive to occur naturally as a free metal. Instead it can be found in over 270 different minerals. The chief ore of aluminum is bauxite which is a mixture of hydrated aluminum oxide (Al 2 O 3+xH 2 O) and hydrated iron oxide (Fe 2 O 3+xH 2 O) (web). Metalic Aluminum was first prepared in 1825 by Hans Oersted, a Danish chemist.
He produced the sample by heating aluminum chloride with Potassium. All 3 + 3 K Al + 3 KCl In the 1850's Robert Bunsen (famous for the Bunsen burner), discovered that aluminum could be obtained by passing an electrical current through molten sodium aluminum chloride. Because of the limited resources of the day not aluminum production would not have been profitable, and aluminum remained specifically. In 1886, Charles Martin Hall of Oberlin, Ohio and Paul Hero ult of France independently discovered the process that is the of method used to produce aluminum (web). The first step in this process is the separation of the of the aluminum oxide from the iron oxide in the bauxite ore.
The separation is accomplished by dissolving the aluminum oxide in a concentrated sodium hydroxide solution. Al 2 O 3 xH 2 O (s) + 2 OH (aq) 2 Al (OH) 4 (aq) + (x 3) H 2 O (l) From there Al (OH) 3 is precipitated from the solution by adding acid. Then the Al (OH) 3 is heated to form alumina Al 2 O 3. Aluminum metal is produced from the electrolytic reduction of alumina (web)...
Pure aluminum appears as a silvery-white metal with many unique and advantageous properties that separate it from other metals. It is incredibly light (density 2.70 g / cm 3), making it a suitable replacement for iron or steel to save weight. It is also non-toxic and easily machined or cast. For added strength it is also easily alloyed (Encarta). Aluminum also weathers far better than iron based on its corrosion properties; Al 2 O 3, adheres strongly to the metal's surface, protecting it from further reaction.
Whereas with iron, rust flakes off the surface of iron, exposing the surface to further corrosion. The oxide coating on aluminum renders it impervious to most acids. However, any chemicals that form a strong complex with aluminum ions, fro example, OH and Cl ions, will react with the oxide coating. Therefore, aluminum will dissolve in hydrochloric acid and sodium hydroxide solutions (web). Recycling of aluminum saves considerable energy. Because the aluminum is already in the metallic state, all of the energy spent in purifying the ore and reducing it to the metal is saved when aluminum is recycled.
The aluminum needs only to be melted to be reused. Aluminum has a rather low melting point, 660. C, and requires only 26 kJ / mol to melt. To reduce a mole of Al from Al 2 O 3 requires over 780 kJ (Encarta). Because of its properties aluminum is a very popular commercial metal, that's production has only become possible in the last hundred and twenty-five years. Aluminum exhibits properties that make it ideal for many forms of casting.
It has a lower melting point that is much simpler to obtain in a melting furnace, unlike steel which requires enormous blast furnaces. For all its uses, engine block, beverage containers, house siding, among others, many could consider this the aluminum age. Peter Smith.