Chemical elements
  Cobalt
    Isotopes
    Energy
    Production
    Preparation
    Application
    Physical Properties
    Chemical Properties
      Hydrogen Occlusion
      Detection
      Estimation
    Compounds
    PDB 1a0c-1epy
    PDB 1et4-1k7y
    PDB 1k98-1r6x
    PDB 1r8k-1v9b
    PDB 1vl3-212d
    PDB 222d-2eff
    PDB 2ehd-2j3z
    PDB 2j4j-2r1p
    PDB 2r2s-331d
    PDB 362d-3fqw
    PDB 3ft6-3igy
    PDB 3igz-3o0n
    PDB 3o0o-4req
    PDB 4xim-9icb

Chemical Properties of Cobalt






Chemical Properties of Cobalt are similar to many metals of this group. Cobalt is not sensibly altered by exposure to air or water at ordinary temperatures, but becomes superficially oxidised at red heat. After being maintained at red heat for some time in an atmosphere of pure nitrogen, the metal becomes less susceptible to attack by nitric acid, possibly because of the formation of a "passive" nitride.

Chemical Properties are very simalar to Iron. Cobalt thus resembles iron in exhibiting passivity, although to a less extent. Concentrated nitric acid attacks it, but acid in the proportion of one part water with two parts concentrated acid dissolves cobalt with extreme slowness.

The metal dissolves slowly in hydrochloric and in dilute sulphuric acid, evolving hydrogen. It combines with chlorine and bromine under the influence of heat, yielding the anhydrous chloride and bromide respectively. Neither cold nor hot solutions of sodium or potassium hydroxide attack cobalt unless the metal is simultaneously made an anode.

Heated in ammonia to about 470° C. cobalt yields a nitride which decomposes at 600° C. Heated in nitrogen peroxide it burns with incandescence, yielding cobalto-cobaltic oxide, Co3O4.

Electrolytic cobalt does not contain nitrogen, and yields no ammonia on heating in a current of pure hydrogen, thereby differing from its congeners, iron and nickel.

When obtained in a finely divided state by reduction of its oxides at 250° C. cobalt is pyrophoric. In this condition it decomposes acetylene in the cold, the metal becoming incandescent. A portion of the acetylene polymerises to benzene, whilst the remainder yields carbon and hydrogen.

Reduced at 400° C. the metal is not pyrophoric, but occludes a considerable volume of hydrogen. The reduced metal decomposes carbon monoxide at 350° to 450° C., depositing solid carbon. Thus:

Co + 2CO = Co + CO2 + C.

In this respect, again, cobalt closely resembles iron.

The metal also combines under special conditions with nitrogen peroxide to form nitro-cobalt, Co2(NO2). When heated with silicon in the electric furnace, silicides are produced, whilst warming with carbon monoxide under pressure effects the production of cobalt tetracarbonyl, Co(CO)4. Heated in nitric oxide to 150° C. the metal burns, yielding the monoxide; at red heat it decomposes steam.


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