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 Arsenides






Cobalt alloys readily with arsenic and several compounds have been prepared. On the freezing point curve there is a eutectic point at 916° C. and 30 per cent. As, and maxima occur at 926° C., 959° C. and 1180° C., corresponding respectively with Co5As2 (33.7 per cent. As), Co2As (38.9 per cent. As) and CoAs (about 55 per cent. As). The curve cannot be obtained for higher percentages of arsenic owing to volatilisation of the latter. The existence of a fourth arsenide, Co3As2, which dissociates without melting at 1014° C., is also indicated. Alloys containing from 12 to 46 per cent. As undergo a transformation on cooling, heat being evolved at temperatures ranging from 250° to 350° C., and a maximum heat development occurs at the composition Co2As, when the transformation point is 352° C. The change is accompanied by a considerable increase in volume and the alloy is sometimes disrupted. The transformation temperatures for the definite arsenides Co5As2 and Co3As2 are respectively 828° and 915° C. Alloys containing up to 38 per cent, arsenic are magnetic; with more than this proportion they are non-magnetic. The addition of arsenic to cobalt causes increased hardness. Other arsenides of composition Co2As3, CoAs2, Co2As5 and CoAs3 have been described.


Tri-cobalt Di-arsenide, Co3As2

Tri-cobalt Di-arsenide, Co3As2, may be prepared by the action of arsenic trichloride on metallic cobalt at 800° to 1400° C.; or by heating mixtures of arsenic and cobalt in hydrogen or carbon monoxide at this temperature. It is also formed when powdered cobalt is heated in hydrogen containing arsenic vapour, and when cobalt arsenate or arsenite is reduced by hydrogen at 900° C. Its density is 7.82 at 0° C. When strongly heated it loses arsenic. It is only slowly attacked by fused alkali, or by hot concentrated hydrochloric or sulphuric acid. It dissolves readily in nitric acid or aqua regia, and reacts vigorously with oxygen, sulphur or chlorine.

Cobalt Monarsenide, CoAs

Cobalt Monarsenide, CoAs, is obtained when the previous compound is heated at 600° to 800° C., when cobalt is heated to 275° to 335° C. in arsenic vapour, or when the elements in equal molecular proportions are heated for not less than a day at 730° C. It is a grey crystalline powder, of density 7.62 at 0° C., tarnishing slightly in the air. It melts at 1180° C. When strongly heated in hydrogen it loses arsenic. It resembles the arsenide Co3As2 in chemical properties. The lattice structure resembles that of the corresponding manganese and iron arsenides, the metal atoms forming zigzag chains, thus differing from nickel monarsenide, in which the metal atoms form straight rows.

Di-cobalt Tri-arsenide, Co2As3

Di-cobalt Tri-arsenide, Co2As3, is formed when cobalt monarsenide is heated at 400° to 600° C., or when cobalt is heated with arsenic trichloride at the same temperature. According to Beutell and Lorenz, it is formed when cobalt is heated in arsenic vapour at 345° to 365° C., but it slowly undergoes decomposition below 400° C. to form the di-arsenide, CoAs2. It also decomposes when heated above 600° C. The density is 7.35 at 0° C.

Cobalt Di-arsenide, CoAs2

Cobalt Di-arsenide, CoAs2, is formed when cobalt is heated in arsenic vapour at 385° to 405° C. Its density is 6.97 at 0° C. It is grey in colour, slightly oxidised by air, and decomposes above 400° C. This arsenide occurs in two forms in Nature, smaltite (cubic), an important ore of cobalt, and safflorite (rhombic).

Cobalt Tri-arsenide, CoAs3

Cobalt Tri-arsenide, CoAs3, is found in Nature as the mineral skutterudite, and is formed when cobalt is heated in arsenic vapour at 450° to 618° C.
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