October 31 - November 3, 2004
Element of the Day
Sunday, October 24
Cobalt
is derived from the German word for goblin or evil spirit, kobald and the Greek
word for mine, cobalos.
Discovered by: Georg Brandt, a Swedish chemist, in 1739. Brandt was attempting to prove that the ability of certain minerals to color glass blue was due to an unknown element and not to bismuth, as was commonly believed at the time.
Uses: Although cobalt is used in electroplating to give objects an attractive surface that resists oxidation, it is more widely used to form alloys. Alnico, an alloy consisting of aluminum, nickel and cobalt is used to make powerful permanent magnets. Stellite alloys, which contain cobalt, chromium and tungsten, are used to make high-speed and high temperature cutting tools and dyes. Cobalt is also used to make alloys for jet engines and gas turbines, magnetic steels and some types of stainless steels.
Cobalt-60, a radioactive isotope of cobalt, is an important source of gamma rays and is used to treat some forms of cancer and as a medical tracer. Cobalt-60 has a half-life of 5.27 years and decays into nickel-60 through beta decay.
Cobalt compounds have been used for centuries to color porcelain, glass, pottery, tile and enamel. Some of these compounds are known as: cobalt blue, ceruleum, new blue, smalt, cobalt yellow and cobalt green. In addition to being used as a dye, cobalt is also important to human nutrition, as it is an essential part of vitamin B12.