Cobalt is a brittle, hard, silver-grey transition metal with magnetic properties similar to those of iron (ferromagnetic). Cobalt is present in meteorites. Ore deposits are found in Zaire, Morocco and Canada. The isotope cobalt-60 (60Co) is an artificially produced isotope used as a source of γ rays (its high energy radiation is useful for sterilisation in medicine and of foods). Cobalt salts colour glass a beautiful deep blue colour. Cobalt compounds are important catalysts in a number of industrial processes. Cobalt is required in small amounts for life and is the only metal found in vitamins (cobalt is the critical component of vitamin B12.
Marmite, which we eat here in England and love it or hate it is a source of vitamin B12, actually a cobalt complex. The equivalent, but blander, in Australia is Vegemite. Marmite is available in the USA. Try mixing it with peanut butter.
Cobalt salts in small amounts are essential to many life forms, including humans. It is at the core of a vitamin called vitamin-B12. Grazing animals do not to do well in areas where there is little cobalt in the soil.
Isotope abundances of cobalt with the most intense signal set to 100%.
Naturally occurring cobalt consists of a single stable isotope:59Co. Cobalt-59 has spin7/2. The usual NMR reference is K3[Co(CN)6] in D2O. Cobalt-60 is an artifical isotope, and is an important γ-ray source.
Isolation: it is not normally necessary to make cobalt in the laboratory as it is available readily commercially. Many ores contain cobalt but not many are of economic importance. These include the sulphides and arsenides linnaeite, Co3S4, cobaltite, CoAsS, and smaltite, CoAs2. Industrially, however, it is normally produced as a byproduct from the produstion of copper, nickel, and lead.
Normally the ore is "roasted" to form a mixture of metals and metal oxides. Treatment with sulphuric acid leaves metallic copper as a residue and disolves out iron, cobalt, and nickel as the sulphates. Iron is obtained by precipitation with lime (CaO) while cobalt is produced as the hydroxide by precipitation with sodium hypochlorite (NaOCl)
Density of solid: 8900 kg m-3
Molar volume: 6.67 cm3
Thermal conductivity: 100 W m‑1 K‑1
Melting point: 1768 [1495 °C (2723 °F)] K
Boiling point: 3200 [2927 °C (5301 °F)] K
Enthalpy of fusion: 20.5 kJ mol-1
Atomic radius (empirical): 135 pm
Molecular single bond covalent radius: 111 (coordination number 4) ppm
van der Waals radius: 240 ppm
Pauling electronegativity: 1.88 (Pauling units)
Allred Rochow electronegativity: 1.70 (Pauling units)
Mulliken-Jaffe electronegativity: (no data)
First ionisation energy: 760.40 kJ mol‑1
Second ionisation energy: 1648.39 kJ mol‑1
Third ionisation energy: 3232.3 kJ mol‑1
Universe: 3000 ppb by weight
Crustal rocks: 30000 ppb by weight
Human: 20 ppb by weight
