Chemical elements
  Cobalt
    Isotopes
    Energy
    Production
    Preparation
    Application
    Physical Properties
    Chemical Properties
    Compounds
      Cobaltous Fluoride
      Hydrated Cobaltous Fluoride
      Cobaltic Fluoride
      Cobaltous Chloride
      Cobaltic Chloride
      Cobaltous Bromide
      Cobaltous Iodide
      Cobalt Oxy-fluoride
      Cobalt Oxy-chloride
      Cobalt Chlorate
      Cobalt Perchlorate
      Cobalt Bromate
      Cobalt Iodate
      Cobalt Monoxide
      Cobaltous Hydroxide
      Tri-cobalt Tetroxide
      Cobalt Sesquioxide
      Hydrated Cobaltic Oxide
      Cobalt Dioxide
      Cobalt Monosulphide
      Tricobalt Tetrasulphide
      Cobalt Sesquisulphide
      Cobalt Disulphide
      Cobalt Polysulphides
      Cobaltous Sulphite
      Cobaltic Sulphite
      Cobalt Thiosulphate
      Cobalt Dithionate
      Cobalt Sulphate
      Ammonium Cobalt Sulphate
      Potassium Cobalt Sulphate
      Cobaltic Sulphate
      Ammonium Cobalt Alum
      Potassium Cobalt Alum
      Cobalt Subselenide
      Cobalt Selenide
      Tricobalt Tetraselenide
      Cobalt Sesquiselenide
      Cobalt Diselenide
      Cobalt Selenite
      Cobalt Diselenite
      Cobalt Triselenite
      Cobaltous Selenate
      Cobaltic Selenate
      Cobalt Sesquitelluride
      Cobalt Tellurite
      Cobalt Chromate
      Cobalt Dichromate
      Double Chromates
      Cobalt Molybdate
      Cobalt Nitride
      Cobalt Azoimide
      Nitro-cobalt
      Potassium Cobaltous Nitrite
      Potassium Cobalti-nitrite
      Sodium Cobalti-nitrite
      Sodium Potassium Cobalti-nitrite
      Ammonium Cobalti-nitrite
      Barium Cobalti-nitrite
      Red Sodium Cobalti-nitrite
      Red Barium Cobalti-nitrite
      Red Strontium Cobalti-nitrite
      Zinc Cobalti-tri-nitrite
      Silver Cobalti-tri-nitrite
      Cobalto-cobalti-tri-nitrite
      Cobaltous Nitrate
      Cobaltic Nitrate
      Cobalt Subphosphide
      Cobalt Sesquiphosphide
      Tri-cobalt Diphosphide
      Tetra-cobalt Triphosphide
      Cobalt Hypophosphite
      Cobalt Phosphite
      Cobalt Metaphosphate
      Tri-cobalt Di-arsenide
      Cobalt Monarsenide
      Cobalt Tri-arsenide
      Cobalt Arsenites
      Cobalt Arsenates
      Cobalt Antimonide
      Cobalt Di-antimonide
      Cobalt Antimonate
      Cobalt Thio-antimonite
      Cobalt Carbide
      Cobalt Tetra-carbonyl
      Cobaltous Carbonate
      Basic Cobaltous Carbonates
      Cobaltic Carbonate
      Cobaltous Cyanide
      Potassium Cobalto-cyanide
      Nickel Cobalto-cyanide
      Cobaltous Cobalto-cyanide
      Zinc Cobalto-cyanide
      Cobalti-cyanic Acid
      Ammonium Cobalti-cyanide
      Barium Cobalti-cyanide
      Potassium Cobalti-cyanide
      Cobalt Cobalti-cyanide
      Cupric Cobalti-cyanide
      Ferrous Cobalti-cyanide
      Nickel Cobalti-cyanide
      Silver Cobalti-cyanide
      Lead Cobalti-cyanide
      Sodium Cobalti-cyanide
      Cobalt Thiocyanate
      Cobalt Subsilicide
      Cobalt Monosilicide
      Cobalt Disilicide
      Cobalt Orthosilicate
      Cobalt Fluosilicate
    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

Cobaltous Hydroxide, Co(OH)2






When potassium hydroxide is added to an aqueous solution of a cobaltous salt, carefully freed from air, a blue precipitate is obtained which, on heating, is converted into the rose-coloured hydroxide - Cobaltous Hydroxide, Co(OH)2.

The blue precipitate was at one time regarded as a basic salt, but Hantzsch showed that any basic salt can be washed out without impairing the colour of the mass. It may be completely dehydrated at 170° C., whereas the pink hydroxide retains some water even after prolonged exposure to 300° C. in an atmosphere of nitrogen. The formula suggested for the blue compound is, accordingly, CoO.H2O, and for the pink one, Co(OH)2.

Cobalt hydroxide dissolves in ordinary distilled water to the extent of 3.18 mgs. of Co(OH)2 per litre at 20° C.

Like its ferrous analogue, cobalt hydroxide readily absorbs oxygen, yielding a brown mass. When dissolved in acids stable cobaltous salts are obtained, but when dissolved in hot, concentrated aqueous potassium hydroxide and allowed to cool, cobaltous oxide gradually crystallises in microscopic prisms which are deposited as a violet powder. The crystals are pleochroic, of density 3.597 at 15° C., permanent in air and insoluble in ammonium hydroxide. They are soluble in acetic acid, in sodium hydroxide, and in hot solutions of ammonium chloride.


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