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

Barium Arsenates





Barium orthoarsenate, Ba3(AsO4)2

Barium orthoarsenate, Ba3(AsO4)2, is formed as large colourless plates when a mixture of barium oxide, alkali chloride and alkali hydrogen orthoarsenate is fused and allowed to cool. It is also said to be formed by the action of ammonia on an aqueous solution of barium hydrogen arsenate; the product, however, varies in composition, barium ammonium arsenate sometimes being formed and barium orthoarsenate rarely. The latter salt retains water, which may be expelled at 150° C.; definite hydrates have not been obtained. It is only slightly soluble in cold water. The anhydrous orthoarsenate has density 5.095 and melts at 1605° C. It is reduced by hydrogen at 400° to 450° C. to barium oxide, arsenic and water.

A study of the acid section of the system As2O5-BaO-H2O at 30° C. shows that the stable solid phases are barium monohydrogen orthoarsenate, BaHAsO4. H2O, barium dihydrogen orthoarsenate, Ba(H2AsO4)2.2H2O, and the (3, 5)-hydrate of arsenic pentoxide, 3As2O5.5H2O.


Barium Monohydrogen Orthoarsenate

Barium Monohydrogen Orthoarsenate may be obtained as a gelatinous precipitate by adding baryta-water drop by drop to aqueous arsenic acid until the solution is alkaline to phenolphthalein. On shaking, the precipitate becomes crystalline. Berzelius obtained this salt in the form of small crystalline scales by adding sodium hydrogen arsenate drop by drop to excess of barium chloride solution. The precipitate may be dried at 100° C. The crystals are transparent rhombic plates of density 3.926 at 15° C.; from acetic acid it may be recrystallised in the form of octahedra. When heated at 120° C. the salt loses its water of crystallisation, and at 320° C. it loses constitutional water and forms barium pyroarsenate.

Barium Dihydrogen Orthoarsenate

Barium Dihydrogen Orthoarsenate crystallises as the dihydrate from a solution of barium orthoarsenate or barium monohydrogen orthoarsenate in aqueous arsenic acid, or it may be precipitated by the addition of baryta-water or barium carbonate to aqueous arsenic acid. The crystals are monoclinic, with axial ratios a:b:c = 1.160:1:0.625 and β = 108°34'. The salt is only slightly soluble in water and in the presence of excess of water changes to the monohydrogen arsenate. It is readily soluble in hydrochloric acid; less soluble in acetic acid. When heated, it loses water, and above 230° C. barium metarsenate, Ba(NaO3)2, remains. The latter may also be obtained by evaporation of a solution of the pyroarsenate and calcination of the residue.

Barium Pyroarsenate, Ba2As2O7

Barium Pyroarsenate, Ba2As2O7, is formed when barium monohydrogen orthoarsenate is ignited, or when barium oxide is fused with an alkali hydrogen arsenate. In the latter case it may be extracted with anhydrous glycerol. In contact with cold water the heccahydrate, Ba2As2O7.6H2O, is formed; boiling water converts it to the orthoarsenate.

Mixed orthoarsenates

Mixed orthoarsenates of composition BaKAsO4, BaNaAsO4.9H2O, Ba(NH4)AsO4H2O and Ba(NH4)2H2(AsO4)2 have been prepared, as also have complex alumini- and ferri-arsenates of composition BaH4[Al(AsO4)3].H2O and Ba3H6[Fe(AsO4)3]2. Barium chlorarsenoapatite, 3Ba3(AsO4)2.BaCl2, can be obtained by fusing a mixture of barium oxide, an alkali chloride and potassium or sodium metarsenate containing more than 60 per cent, of the arsenate. Bromo- and iodo-arsenoapatites are also known.

Complex pyroarsenates

Complex pyroarsenates of composition BaCuAs2O7 and BaHgAs2O7. H2O have been obtained by heating aqueous solutions of arsenic acid with mixtures of barium hydroxide and the oxide or carbonate of the other metal at 180° to 200° C. Using copper carbonate and solutions of arsenic acid of 5 to 25 per cent, concentration, the barium-copper salt is formed quantitatively and the precipitate is of constant composition, but outside the above limits of acid concentration the precipitate consists mainly of a mixture of orthoarsenates.
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