Chromium is a very hard, brittle, gray metal, which is sometimes
referred to as Siberian red lead. It does not rust easily and becomes shiny and
bright when it is polished. The shiny trim on our automobile bumpers and door
handles is usually electroplated chromium.
Most chromium comes from something called chromite which is a mixture
, iron, and oxygen. Chromite is a common rather ordinary black
mineral that no one really noticed until more recent times. Nearly all the
world's supply of chromite comes from Zimbabwe, Russia, Turkey, South Africa,
Cuba, and the Philippines. The United States imports almost all its chromite.
Chromium is added to other metals to make them harder and more
resistant to chemicals. Small quantities mixed with steel make the metal
stainless. Stainless steel is used to make cutlery and kitchen equipment
because it does not rust easily and takes a mirror-like polish. This steel
contains about 13 percent chromium and 0.3 percent carbon. The hardness of steel
can be increased by adding small quantities of chromium to it. Chromium steel
alloys (mixtures containing one or more metals) are used to make armor plating
for tanks and warships. They are also used for ball bearings and the hard
cutting edges of high-speed machine tools.
Nickel is highly resistant to electric current
and is often added to
chromium steels to make them easier to work. For example, stainless steel
sinks can be pressed out from flat sheets of steel that can contain 18 percent
chomium and 8 percent nickel.
When nickel is mixed with chromium, the resulting metal can stand
very high temperatures without corroding. For example, the heating elements of
toasters can be made from an alloy that is 80 percent nickel and 20 percent
chromium. This metal operates at a temperature of about 1380 degrees
Fahrenheit (750 degrees Celsius).
Chromium was discovered in 1798 by the French chemist Nicolas
Vauquelin. He chose the name chromium from the Greek word chroma, which means
color. Chromium was a good choice of name, many chromium compounds are brightly
colored. Rubies are red and emeralds are green because they contain chromium
Some of the brightest colors in the artist's palette contain chromium.
Chrome yellow is made from a substance which contains chromium, lead, and
oxygen. Zinc yellow contains zinc, chromium and oxygen. Chrome red is another
chromium compound. Chrome green is used in paints and in printing cotton
Chromium salts are used in tanning leather. Leather tanned in this
way is very soft and flexible. It is used in the manufacture of soft gloves
and other luxury goods. Other chromium compounds are used to treat metal and
wood. This treatment helps to preserve objects from corrosion and rot.
Chromium is an element wit the chemical symbol Cr, an atomic weight
of 51.996. Although it is twice as heavy as aluminum, it is lighter tan all
other common metals. It melts at a temperature of 3434 degrees Fahrenheit (1890