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 of chromium, 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 compounds. 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 fabrics. 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 with 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 degrees Celsius).
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