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a chemical element, atomic number 27, atomic weight 58.933. (See Appendix 6.)
cobalt 57 a radioisotope of cobalt, atomic mass 57, having a half-life of 270 days; used as a label for cyanocobalamin. Symbol 57Co.
cobalt 60 a radioisotope of cobalt, atomic mass 60, having a half-life of 5.27 years and a principal gamma ray energy of 1.33 MeV; used as a radiation therapy source. Symbol 60Co.
co·balt 60 (60Co),(kō'bawlt),
Half-life, 5.271 years; emits beta particles and energetic gamma rays, for which reason it is used in radiation teletherapy and diagnostics in place of radium, radon, or x-rays. It is also used as a diagnostic aid in the evaluation of vitamin B12 absorption.
Radioactive isotope created by irradiating stable 59Co with neutrons in a reactor; has a mass number of 60; half-life 5.3 years; used in teletherapy and brachytherapy; emits beta particles and gamma-rays.