Chemical elements
  Arsenic
      Occurrence
      Ubiquity
      History
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
      Aluminium Arsenide
      Antimony Arsenides
      Barium Arsenide
      Bismuth Arsenides
      Cadmium Arsenides
      Calcium Arsenide
      Cerium Arsenide
      Chromium Arsenides
      Cobalt Arsenides
      Copper Arsenides
      Gold Arsenides
      Iridium Arsenide
      Iron Arsenides
      Lead Arsenides
      Lithium Arsenide
      Magnesium Arsenide
      Manganese Arsenides
      Mercury Arsenides
      Molybdenum Arsenide
      Nickel Arsenides
      Niobium Arsenide
      Palladium Di-arsenide
      Platinum Arsenides
      Potassium Arsenides
      Rhodium Arsenide
      Ruthenium Arsenide
      Silver Arsenides
      Sodium Arsenide
      Strontium Arsenide
      Thallium Arsenide
      Tin Arsenides
      Tungsten Arsenide
      Uranium Arsenide
      Zinc Arsenides
      Arsenic Subhydride
      Arsenic Monohydride
      Arsenic Trihydride
      Arsenic Trifluoride
      Arsenic Pentafluoride
      Arsenic Nitrosyl Hexafluoride
      Arsenic Trichloride
      Arsenic Oxychloride
      Arsenic Pentachloride
      Arsenic Tribromide
      Arsenic Oxybromide
      Arsenic Moniodide
      Arsenic Diiodide
      Arsenic Triiodide
      Arsenic Pentiodide
      Arsenic Suboxide
      Arsenious Oxide
      Aluminium Arsenite
      Ammonium Arsenites
      Antimony Arsenite
      Barium Arsenites
      Beryllium Arsenite
      Bismuth Arsenite
      Cadmium Arsenites
      Calcium Arsenites
      Chromic Arsenite
      Cobalt Arsenites
      Copper Arsenites
      Gold Arsenites
      Iron Arsenites
      Lead Arsenites
      Lithium Arsenite
      Magnesium Arsenites
      Manganese Arsenites
      Mercury Arsenites
      Nickel Arsenites
      Palladium Pyroarsenite
      Platinum Arsenites
      Potassium Arsenites
      Arsenites of Rare Earth Metals
      Rubidium Metarsenite
      Silver Arsenites
      Sodium Arsenites
      Strontium Arsenites
      Thallous Orthoarsenite
      Tin Arsenites
      Titanyl Tetrarsenite
      Tungsto-arsenites
      Uranyl Metarsenite
      Zinc Arsenites
      Zirconium Arsenite
      Arsenic Tetroxide
      Arsenic Pentoxide
      Aluminium Arsenates
      Ammonium Arsenates
      Barium Arsenates
      Beryllium Arsenates
      Bismuth Arsenates
      Cadmium Arsenates
      Caesium Arsenate
      Calcium Arsenates
      Chromium Arsenates
      Cobalt Arsenates
      Copper Arsenates
      Hydroxylamine Orthoarsenate
      Iron Arsenates
      Lead Arsenates
      Lithium Arsenates
      Magnesium Arsenates
      Manganese Arsenates
      Mercury Arsenates
      Molybdenum Arsenates
      Nickel Arsenates
      Palladium Arsenate
      Platinic Arsenate
      Potassium Arsenates
      Rare Earth Metals Arsenates
      Rhodium Arsenate
      Rubidium Arsenates
      Silver Arsenates
      Sodium Arsenates
      Strontium Arsenates
      Thallium Arsenates
      Thorium Arsenates
      Tin Arsenates
      Titanyl Arsenate
      Tungsto-arsenic Acids
      Uranium Arsenates
      Vanado-arsenates
      Zinc Arsenates
      Zirconium Arsenates
      Perarsenates
      Arsenic and Sulphur
      Arsenic Subsulphide
      Tetrarsenic Trisulphide
      Arsenic Disulphide
      Arsenic Trisulphide
      Arsenic Pentasulphide
      Thioarsenates
      Ammonium Thioarsenates
      Antimony Thioarsenate
      Barium Thioarsenates
      Beryllium Thioarsenate
      Bismuth Thioarsenate
      Cadmium Thioarsenates
      Calcium Thioarsenates
      Cerium Thioarsenates
      Chromium Thioarsenate
      Cobalt Thioarsenate
      Copper Thioarsenates
      Gold Thioarsenates
      Iron Thioarsenates
      Lead Thioarsenates
      Lithium Thioarsenates
      Magnesium Thioarsenates
      Manganese Thioarsenates
      Mercury Thioarsenates
      Molybdenum Thioarsenates
      Nickel Thioarsenates
      Platinic Thioarsenate
      Potassium Thioarsenates
      Silver Thioarsenates
      Sodium Thioarsenates
      Strontium Thioarsenates
      Thallium Orthothioarsenate
      Tin Thioarsenates
      Uranyl Thioarsenate
      Yttrium Thioarsenate
      Zinc Thioarsenates
      Zirconium Thioarsenate
      Trioxythioarsenic Acid
      Dioxydithioarsenic Acid
      Oxytrithioarsenic Acid
      Arsenic Monosulphatotrioxide
      Arsenic Disulphatotrioxide
      Arsenic Trisulphatotrioxide
      Arsenic Tetrasulphatotrioxide
      Arsenic Hexasulphatotrioxide
      Arsenic Octasulphatotrioxide
      Complex salts of Sulphato-compounds of Arsenic
      Arsenic Nitride
      Arsenic Imide
      Arsenic Amide
      Arsenic Phosphides
      Arsenic oxyphosphides
      Arsenic Phosphate
      Arsenic Thiophosphate
      Arsenic Tricarbide
      Arsenic Pentasilicide
      Boron Arsenate
    Detection of Arsenic
    Estimation of Arsenic
    Physiological Properties
    PDB 1b92-1ihu
    PDB 1ii0-1tnd
    PDB 1tql-2hmh
    PDB 2hx2-2xnq
    PDB 2xod-3htw
    PDB 3hzf-3od5
    PDB 3ouu-9nse

Cobalt Arsenates





Cobalt Orthoarsenate, Co3(AsO4)2

Cobalt Orthoarsenate, Co3(AsO4)2.8H2O, may be precipitated as pink microscopic needles by adding ammonium orthoarsenate to an aqueous solution of a cobalt salt, or by stirring cobalt oxide or carbonate with aqueous arsenic acid. It occurs widely distributed in Nature as the mineral erythrite or cobalt bloom in the form of monoclinic crystals isomorphous with vivianite, Fe3(PO4)2. 8H2O, and perhaps with nickel ochre, Ni3(AsO4)2.8H2O. Its crystal-lographic elements are a:b:c = 0.7937:1:0.7356; β = 74°51'. The indices of refraction along the three axes for sodium light are a = 1.629, β = 1.663 and γ = 1.701. The mineral is soluble in hydrochloric acid forming a blue solution which reddens on dilution. A cobalt hydrogen arsenate of composition Co2H2(AsO4)2.3.5H2O is precipitated by adding ether to a mixture of syrupy arsenic acid (2 parts) and alcoholic cobalt nitrate (3 parts). The salt readily loses water. Cobalt dihydrogen tetrarsenate, Co3(AsO4)2.2CoHAsO4.2H2O, has been obtained as red needle-shaped crystals by heating excess of arsenic acid with cobalt carbonate in a sealed tube at 235° C. It is insoluble in water and loses its water of crystallisation when heated.


Basic cobalt arsenate Co3(AsO4)2,CoO

A basic arsenate of composition Co3(AsO4)2.CoO is obtained when sodium carbonate is added to a solution of cobalt orthoarsenate in nitric acid and the precipitate heated to fusion. On cooling, deep blue prismatic crystals are formed which, when powdered, turn a rose-red colour. The product, which is soluble in acids, has been used as a pigment. An impure basic arsenate is known under the name of zaffre and is used in painting porcelain. It may be obtained by roasting iron-free cobaltite, or by addition of sodium carbonate to a solution of cobaltite in nitric acid, when the zaffre is obtained as a precipitate. A salt of composition 5CoO.2As2O5.15H2O (and also with 28H2O) has been prepared.

Cobalt Pyroarsenate, Co2As2O7

Cobalt Pyroarsenate, Co2As2O7, is formed when cobalt oxide is fused with potassium metarsenate; violet crystals are obtained on cooling. A dihydrate, Co2As2O7.2H2O, has also been described.

Ammino-orthoarsenates of cobalt

Ammino-orthoarsenates of composition Co3(AsO4)2(NH3).7H2O, Co3(AsO4)2(NH3)2.6H2O and Co3(AsO4)2(NH3)3.5H2O have been obtained by the interaction in solution of a cobalt salt, arsenic acid or an arsenate and free ammonia, ammonium salts being present. The nature of the product depends on the amount of free ammonia present.

Colloidal cobalt arsenate

Colloidal cobalt arsenate has been obtained in the form of an opalescent jelly either by mixing in the cold a solution of a cobalt salt of a strong acid with potassium dihydrogen orthoarsenate, or by successively treating an aqueous solution of a cobaltous salt with ammonium sulphate, acetic acid and an excess of sodium orthoarsenate.

Mixed cobalt arsenates

The following mixed arsenates have been prepared: NaCoAsO4, KCoAsO4, Na4Co4As6O21. Complex salts corresponding to the ferri-arsenates do not appear to be formed
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