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Cobalt has been in use as a coloring agent for glass since ancient times. The most imporant use of cobalt is in the manufacture of various wearresistant and superalloys. Its alloys have shown high resistance to corrosion and oxidation at high temperatures. They are used in machine components. Also, certain alloys are used in desulfurization and liquefaction of coal and hydrocracking of crude oil shale. Cobalt catalysts are used in many industrial processes. Several cobalt salts have wide commercial applications Cobalt oxide is used in glass to impart pink or blue color. Radioactive cobalt–60 is used in radiography and sterilization of food.
Cobalt is a silvery-gray brittle but hard metal, which is distributed widely in nature, including rocks, soil, plants, and animals. It is a metal with no odor and no vapor pressure at room temperature and is insoluble in water, except for ultrafine cobalt powder, which is water soluble. It is stable in air but chemically reactive with dilute acids and is a nonvolatile metal. Required in small amounts, cobalt is important for the sustenance of life. It is the only metal found in vitamins, most importantly as a part of vitamin B12 and is necessary in the formation of blood. Cobalt is a component of many naturally occurring minerals like sulfides, hydrates, and oxides. Cobalt compounds can occur in various oxidation states (0, +1, +2, +3, and +4) but the most common oxidation states are +2 and +3. Cobalt has one naturally occurring isotope, cobalt-59 and 26 radioactive isotopes.