Cobalt

Key information
Atomic number: 
27
Atomic weight: 
59
Density: 
8900 kg/m³
Boiling point: 
3173.16° K
Melting point: 
1768.16° K
Heat vapour: 
389.45 kJ/mol
Heat fusion: 
15.24 kJ/mol
Thermal conductivity: 
16 W/m/K
Specific heat capacity: 
67 J/kg/K

In 1735 Georg Brandt (1694-1768) identified some properties of cobalt. Antoine Lavoisier (1743-1794) in his Traité Élémentaire de Chimie (Elementary Treatise of Chemistry, 1789) included a list of elements, or substances that could not be broken down further, which included cobalt.

Cobalt is a strategic metal with very important applications, including those requiring heat-resistant materials such as jet engines. The major source of cobalt is as a by-product of copper refining although it can also be obtained as a by-product of nickel and lead.

Cobalt(III) complexes display a range of colours including the pigment cobalt blue:

  1. [CoF6]3- - Green
  2. [Co(NH3)5Cl]2+ - Violet
  3. [Co(H2O)6]3+ - Blue
  4. [Co(NH3)5(H2O]3+ - Red
  5. [Co(NH3)6]3+ - Yellow-orange
  6. [Co(CN6]3- - Tail of absorption band in visible spectrum is yellow

Cobalt ores were first used by the ancient Egyptians for colouring glass, and by the Persians for making blue enamels and glazes.

Chartres Cathedral

To create coloured glass, required in the stained glass windows of Chartres Cathedral in France, metal oxide powders were added to the melted glass, their atoms bonding into the silicon/oxygen glass lattices: blue colours were provided by cobalt.

Valency: 
Amazon Books
Image of The Last Sorcerers: The Path from Alchemy to the Periodic Table
Author: Richard Morris
Publisher: Joseph Henry Press (2003)
Binding: Hardcover, 296 pages