Cobalt is a silver-white metallic element that has properties similar to those of iron and nickel. All three metals are hard and magnetic. Cobalt is used chiefly in alloys (mixtures of metals).
Cobalt’s atomic number (number of protons in its nucleus) is 27. Its relative atomic mass is 58.933200. An element’s relative atomic mass equals its mass (amount of matter) divided by 1/12 of the mass of an atom of carbon 12, the most abundant form of carbon. Cobalt has a density of 8.9 grams per cubic centimeter. It melts at a temperature of 1495 °C. It boils at 2870 °C. Its chemical symbol is Co. The Swedish chemist Georg Brandt first isolated cobalt in the 1730’s.
Chemists classify cobalt as a transition metal . For information on the position of cobalt on the periodic table, see the article Periodic table .
Sources.
Cobalt makes up only about 30 millionths of the mass of Earth’s crust. It occurs in cobalt ores in chemical compounds with arsenic, oxygen, or sulfur. Those cobalt compounds also occur in nickel, iron, and copper ores. Zambia and the Democratic Republic of the Congo have more than half the world’s reserves of cobalt ores. Other major deposits lie in Australia, Azerbaijan, Canada, Cuba, Finland, Kazakhstan, and New Caledonia.
Uses.
Cobalt is combined with carbon and tungsten or with chromium, iron, and other metals to create hard alloys for drill bits and cutting tools. Cobalt alloys that withstand high temperatures are used in gas turbines and jet engines. Alloys of cobalt are also used in dental and surgical applications due to their stability.
Cobalt alloys with aluminum, nickel, iron, or other metals are used in strong permanent magnets., Such magnets do not lose their magnetization. Cobalt magnets are used in magnetic resonance imaging (MRI) machines, electronic devices, and speakers.
Cobalt oxides (compounds that include cobalt and oxygen) have been used since ancient times as pigments. Cobalt oxides add deep blue color to pottery, glass, and enamels. They are also used in artists’ blue paints, inks, and dyes. The paint industry uses cobalt salts to speed drying of paints, lacquers, and varnishes. A salt is a compound that results when a base neutralizes an acid (see Salt, Chemical ). Other uses of cobalt salts are electroplating and the bonding of rubber to steel in tires.
Cobalt catalysts aid in the production of liquid fuels and organic compounds from petroleum. Catalysts are substances that increase the speed of a chemical reaction. Vitamin B 12 contains cobalt. Vitamin B 12 is needed to help nerve cells function properly. The vitamin also helps red blood cells form in bone marrow.
Physicians use cobalt 60, a radioactive isotope (form) of cobalt, to treat cancer patients. Some food-processing plants use radiation from cobalt 60 to kill bacteria in foods.
