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Roger Weller, geology instructor
by Michelle Padilla
The element chromium, atomic
number 24, is a hard metal with a shiny surface. The metallic luster of this
material makes it appealing to the eye, one of the reasons it is often used as a
steal coating. Chromium, also known as chrome, is a solid material at room
Chromium is found in the form of ores. In order to separate the
metal, the chromite ore (FeCr2O4) is oxidized to chromium oxide (Cr2O3), the
metal is then separated by heating the oxide with aluminum or silicon. Though it
is rare, native chromium can be found in kimberlite pipe. As the 21st
most abundant element, it is present at about 100ppm concentration. It has a
melting point of 3464.6°F and a boiling point of 4839.8°F, which makes it a good
material for working around extremely high temperatures.
Louis-Nicholas Vanquelin was the first person in Western
civilization to discover chromium as an element in 1797. During Vanquelins
experimentations with chromium he made many discoveries. He found that it could
change to a multitude of colors in different solutions; because of this he named
the element after the Greek word for color, chroma. The beautiful green color in
emeralds is due to traces of chromium.
A few years later a chemist by the name
of Tassaert discovered chromium in chromite ore, now known as chromite, which is
now a major source of chromium. Though Vanquelins discoveries were the first of
his time, over 2,000 years ago the ancient Chinese used chromium to coat their
weapons, in order to strengthen them and protecting them from tarnishing.
Chromium is rarely found by itself, it is usually found
in chromite ore. Chromite is found in places such as Albania, Finland, Iran,
Madagascar, New Zealand, the Philippines, Russia, Turkey and even Zimbabwe.
Chromite can be found in stratiform deposits (layerd), podiform (pillow-like)
deposits and beach sand. Because Chromium is not mined in the United States,
more than half of the chromium used comes from recycled metal.
Uses of Chromium
As a very corrosion resistant substance, it is used a lot in industrial factories. Chromium can be used to harden steal, this is useful in the equipment used in factories and even in the auto mobile industry for car parts such as bumpers.
However, the first form of chromium
plating was used in jewelry. The use of chromium became very popular in the
1950s because the metallic look was “trendy” The word chrome soon became an
everyday household word in the United States. Prior to the 1950s not many people
knew about chromium or what it was.
Because of the high melting and boiling points, it can be used
work in extreme temperatures such as welding. Chromium has the ability to
maintain its shape without warping in extreme heat, this is why this element can
be used the lining of jet engines. Another place chromium is sometimes used is
in the barrel of guns, as it is necessary for the lining to be able to withstand
the incredible heat set off by the bullets.
Chromium is known for producing beautiful colors, which is why it
is used as an industrial catalysts to add pigments of green, red, orange and
even yellow. As early as the 1820s the most common use for chromium was in the
textile industry. The color was able to bind will with fibers and as a result it
prevented the dye from bleeding. One of the most common uses for this material
is in leather, approximately 90% of all leather in tanned using chrome.
Chromium, though a very useful material, can also be extremely harmful. Though only trace amounts of chromium actually enter the human cells, more recently it has been discovered that a large amount of factory workers who were exposed to hexavalent chromium also showed cases of lung cancer, damage to the nose, throat and lungs, and damage to eyes and skin. Most of these employees likely inhaled hexavalent chromium in the form of dust. These employees could have been exposed to the dangerous fumes while welding, tanning leather of producing chromium pigments. There are some forms of chromium that are more harmful than others; one of those is Chromium (VI) which is carcinogenic and toxic to humans. Many of these industries are now looking into alternatives to using chromium.