Aluminum
The name aluminum is derived from
the ancient name for alum (potassium aluminum sulphate),
which was alumen (Latin, meaning bitter salt).
Aluminum was the original name given to the element by Humphry
Davy but others called it aluminum and that became the accepted name in
Aluminum is a soft and lightweight metal. It has a dull
silvery appearance, because of a thin layer of oxidation that forms quickly
when it is exposed to air. Aluminum is nontoxic (as the metal) nonmagnetic and
non-sparking.
Aluminum has only one naturally occurring isotope, aluminium-27, which is not radioactive.
Applications
A silvery and ductile member of
the poor metal group of elements, aluminum is found primarily as the ore bauxite
and is remarkable for its resistance to oxidation (aluminum is actually almost
always already oxidized, but is usable in this form unlike most metals), its
strength, and its light weight. Aluminum is used in many industries to make
millions of different products and is very important to the world economy.
Structural components made from aluminum are vital to the aerospace industry
and very important in other areas of transportation and building in which light
weight, durability, and strength are needed.
The use of aluminum exceed that of any other metal
except iron. Pure aluminum easily forms alloys with many elements such as
copper, zinc, magnesium, manganese, and silicon. Nearly all modern mirrors are
made using a thin reflective coating of aluminum on the back surface of a sheet
of float glass. Telescope mirrors are also coated with a thin layer of
aluminum.
Other applications are electrical transmission lines, and packaging (cans,
foil, etc.).
Because of its high conductivity and relatively low price compared to copper,
aluminum was introduced for household electrical wiring to a large degree in
the
The most recent development in aluminum technology is the production of
aluminum foam by adding to the molten metal a compound (a metal hybrid), which
releases hydrogen gas. The molten aluminum has to he thickened before this is
done and this is achieved by adding aluminum oxide or silicon carbide fibers.
The result is a solid foam which is used in traffic
tunnels and in space shuttle.
Aluminum in the environment
Aluminum is an abundant element in
Earth's crust: it is believed to be contained in a percentage from 7.5% to
8.1%. Aluminum is very rare in its free form. Aluminum contribute
greatly to the properties of soil, where it is present mainly as insoluble
aluminum hydroxide.
Aluminum is a reactive metal and it is hard to extract it from its ore,
aluminum oxide (Al2O3). Aluminum is among the most
difficult metals on earth to refine, the reason is that aluminum is oxidized
very rapidly and that its oxide is an extremely stable compound that, unlike
rust on iron, does not flake off. The very reason for which aluminum is used in
many applications is why it is so hard to produce.
Several gemstones are made of the clear crystal form of aluminum oxide known as
corundum. The presence of traces of other metals creates various colors: cobalt
creates blues sapphires, and chromium makes red rubies. Both these are now easy
and cheap to manufacture artificially. Topaz is aluminum silicate coloured yellow by traces of iron.
Recovery of this metal from scrap (via recycling) has become an important
component of the aluminum industry. Industrial production world-wide of new
metal is around 20 million tons per year, and a similar amount is recycled.
Known reserves of ores are 6 billion tones.
Health effects of aluminum
Aluminum is one of the most widely
used metals and also one of the most frequently found compounds in the earth's
crust. Due to these facts, aluminum is commonly known as an innocent compound.
But still, when one is exposed to high concentrations, it can cause health
problems. The water-soluble form of aluminum causes the harmful effects, these
particles are called ions. They are usually found in a solution of aluminum in
combination with other ions, for instance as aluminum chlorine.
The uptake of aluminum can take place through
food, through breathing and by skin contact. Long lasting uptakes of
significant concentrations of aluminum can lead to serious health effects, such
as:
- Damage to the central nervous system
- Dementia
- Loss of memory
- Listlessness
- Severe trembling
Aluminum is a risk in certain working environments, such as mines, where it can
be found in water. People that work in factories where aluminum is applied
during production processes may endure lung problems when they breathe in
aluminum dust. Aluminum can cause problems for kidney patients when it
enters the body during kidney dialyses.
Inhalation of finely divided aluminum and aluminum oxide powder has been reported as a cause of pulmonary fibrosis and lung damage. This effect, know as Shaver’s Disease, is complicated by the presence in the inhaled air of silica and oxides of iron. May also be implicated in Alzheimer’s disease.
Environmental effects of aluminum
The effects of
aluminum have drawn our attention, mainly due to the acidifying problems.
Aluminum may accumulate in plants and cause health problems for animals that
consume these plants.
The concentrations of aluminum appear to be
highest in acidified lakes. In these lakes the number of fish and amphibians is
declining due to reactions of aluminum ions with proteins in the gills of fish
and the embryo's of frogs.
High aluminum concentrations do not only cause effects upon fish, but also upon
birds and other animals that consume contaminated fish and insects and upon
animals that breathe in aluminum through air. The consequences for birds that
consume contaminated fish are eggshell thinning and chicks with low
birth-weights. The consequences for animals that breathe in aluminum through
air may be lung problems, weight loss and a decline in activity.
Another negative environmental effect of aluminum is that its ions can react
with phosphates, which causes phosphates to be less available to water
organisms.
High concentrations of aluminum may not only be found in acidified lakes and air,
but also in the groundwater of acidified soils. There are strong indications
that aluminum can damage the roots of trees when it is located in groundwater.