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

Iron Arsenites






Both ferrous and ferric compounds are known, but the existence of ferrous orthoarsenite has not been established. Ferrous metarsenite, Fe(AsO2)2, has been obtained by the action of potassium tetrarsenite, K2As4O7.2H2O, upon a dilute solution of ferrous sulphate. It is greenish in colour, becoming brown on exposure to air. It decomposes when heated. When a hot, saturated solution of arsenious acid containing ferrous iodide is allowed to cool, crystals of the compound FeI2.4As2O3.12H2O are obtained, which slowly oxidise in air, and in vacuo over concentrated sulphuric acid yield up all their combined water. The iodide character of the salt is suppressed, from which it may be inferred that the iodine has combined with the arsenious oxide to yield a complex negative radical.


Ferric Orthoarsenite, FeNaO3

Ferric Orthoarsenite, FeNaO3, was described by Reichard as a rust-yellow powder obtained by adding potassium tetrarsenite to a dilute aqueous solution of ferric chloride. A substance of similar chemical composition has been found in a crystalline deposit formed during the Deacon process of making chlorine. The crystals of the pure salt are monoclinic, their crystallographic elements being:

a:b:c = 0.9405:1:0.6234 β = 105°10.5'

The pentahydrate, FeNaO3.5H2O, found with the preceding salt, crystallises in the rhombic system.

Ferric arsenite is reduced to a slight extent when heated in an inert atmosphere; if heated in hydrogen under pressure it decomposes, forming iron arsenide, iron oxide and arsenious oxide.

On adding freshly precipitated ferric arsenite to potassium hydroxide solution until no more dissolves, and subsequently evaporating, the soluble potassium salt, 6K2O.5Fe2O3.9As2O3.24H2O, is obtained as a reddish-brown amorphous substance, which dissolves in water, yielding an alkaline solution.

Ferric orthoarsenite cannot be prepared directly from ferric hydroxide and arsenious oxide. The brown product obtained by shaking freshly precipitated ferric hydroxide with an aqueous solution of arsenious oxide has been described as a basic ferric arsenite of composition 4Fe2O3.As2O3.5H2O. A similar substance is obtained by adding aqueous arsenious oxide or sodium arsenite to ferric acetate solution. If ferric chloride, sulphate or nitrate is used, the ferric salt is not completely precipitated. The product is oxidised in moist air, and decomposes when heated. It is very doubtful whether this is a chemical individual, however, for it has been shown that the removal of arsenious oxide from the solution by the ferric hydroxide is due to adsorption, the amount removed depending upon the conditions and the age of the adsorbent.

When a mixture of ferric oxide and arsenious oxide is heated, a mixture of orthoarsenite and orthoarsenate is formed above 225° C., and above 600° C. the latter is the sole product.

Ferric Pyroarsenite, Fe4(As2O5)3

Ferric Pyroarsenite, Fe4(As2O5)3.7H2O, has been described as a yellow substance obtained by adding ferric hydroxide to a hot saturated solution of arsenious oxide in concentrated sodium hydroxide. On cooling, excess of arsenious oxide separates, and after keeping for 24 hours a yellow precipitate of the above composition is formed. The existence of the pyroarsenite has not been confirmed, however.
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