Chemical elements
  Tungsten
    Isotopes
    Energy
    Production
    Preparation
    Application
    Physical Properties
    Chemical Properties
    Compounds
      Tungsten Hexafluoride
      Tungsten Oxyfluorides
      Tungsten Dichloride
      Double Chlorides of Trivalent Tungsten
      Tungsten Tetrachloride
      Tungsten Pentachloride
      Tungsten Hexachloride
      Tungsten Oxychlorides
      Tungsten Dibromide
      Tungsten Pentabromide
      Tungsten Hexabromide
      Tungsten Chlorobromides
      Tungsten Oxybromides
      Tungsten Di-iodide
      Tungsten Tetra-iodide
      Tungsten Dioxide
      Ditungsten Pentoxide
      Tungsten Trioxide
      Tungstic Acid
      Aluminium Tungstates
      Ammonium Tungstates
      Antimony Tungstates
      Barium Tungstates
      Normal Bismuth Tungstate
      Cadmium Tungstates
      Calcium Tungstates
      Cerium Tungstate
      Chromium Tungstates
      Cobalt Tungstates
      Copper Tungstates
      Indium Tungstate
      Iron Tungstates
      Lanthanum Tungstate
      Lead Tungstates
      Lithium Tungstates
      Magnesium Tungstates
      Manganese Tungstates
      Mercury Tungstates
      Neodymium Tungstate
      Nickel Tungstates
      Platinum Tungstates
      Potassium Tungstates
      Praseodymium Tungstate
      Rubidium Tungstates
      Samarium Tungstate
      Silver Tungstates
      Sodium Tungstates
      Strontium Tungstates
      Thallium Tungstates
      Tin Tungstates
      Uranium Tungstate
      Ytterbium Tungstates
      Yttrium Tungstate
      Zinc Tungstates
      Metatungstic Acid
      Ammonium Metatungstate
      Barium Metatungstate
      Cadmium Metatungstate
      Calcium Metatungstate
      Cerium Metatungstate
      Cobalt Metatungstate
      Lead Metatungstate
      Magnesium Metatungstate
      Mercurous Metatungstate
      Nickel Metatungstate
      Potassium Metatungstate
      Rubidium Metatungstate
      Samarium Metatungstate
      Silver Metatungstate
      Sodium Metatungstate
      Strontium Metatungstate
      Thallous Metatungstate
      Zinc Metatungstate
      Pertungstic Acid
      Tungsten Bronzes
      Potassium Tungsten Bronze
      Lithium Tungsten Bronze
      Lithium Potassium Tungsten Bronze
      Sodium tungsten bronzes
      Tungsten Disulphide
      Tungsten Trisulphide
      Thiotungstates
      Tungsten Diselenide
      Tungsten Triselenide
      Tungsten Phosphides
      Tungsten Diphosphide
      Tritungsten Tetraphosphide
      Tungsten Monophosphide
      Tungsten Subphosphide
      Phosphotungstic Acids
      12-Tungstophosphoric Acid
      11-Tungstophosphates
      21:2-Tungstophosphoric Acid
      10-Tungstophosphoric Acid
      9-Tungstophosphoric Acid
      17:2-Tungstophosphates
      3-Tungstophosphates
      Hypophosphotungstates
      Tungsten Diarsenide
      Tungsten Chloro-arsenide
      12-Tungsto-arsenates
      11-Tungsto-arsenates
      9-Tungsto-arsenic Acid
      17:2-Tungsto-arsenates
      Tungsto-arsenites
      Tritungsten Carbide
      Ditungsten Carbide
      Tungsten Monocarbide
      Tungsten Iron Carbides
      Tungstocyanic Acid
      Ammonium Tungstocyanide
      Calcium Tungstocyanide
      Cadmium Tungstocyanide
      Caesium Tungstocyanide
      Lead Tungstocyanide
      Magnesium Tungstocyanide
      Manganese Tungstocyanide
      Potassium Tungstocyanide
      Rubidium Tungstocyanide
      Silver Tungstocyanide
      Sodium Tungstocyanide
      Strontium Tungstocyanide
      Thallium Tungstocyanide
      Zinc Tungstocyanide
      Tungsticyanic Acid
      Tungsten Sesquisilicide
      Tungsten Disilicide
      Tungsten Trisilicide
      12-Tungstosilicic Acid
      Iso-12-tungstosilicic Acid
      10-Tungstosilicates
      Tungsten Boride
      12-Tungstoboric Acid
      Iso-12-tungstoboric Acid
    Alloys
    PDB 1aor-2rav
    PDB 2rb5-6fit

12-Tungstoboric Acid, H9[B(W2O7)6]






12-Tungstoboric Acid, H9[B(W2O7)6].28H2O, is prepared by the addition to 1 part of normal sodium tungstate and 1.5 parts of boric acid of sufficient water to form a clear solution on boiling. After a time a mixture of sodium borate and boric acid separates. This is filtered off, the mother-liquor is treated with more boric acid, a further precipitate is rejected, and the solution treated with sulphuric acid and ether according to Drechsel. The resulting oil is decomposed by cold water, and on evaporation in a vacuum, crystals of two isomeric acids separate simultaneously; those in larger quantity being transparent octahedra of 12-tungstoboric acid, H9[B(W2O7)6].28H2O; those in smaller quantity, hexagonal bipyramidal crystals of iso-12-tungstoboric acid, H9[B(W2O7)6].22H2O. The first acid is isomorphous with the 28-hydrates of the 12-tungsto- and 12-molybdo-phosphoric and silicic acids. It melts at 45° to 51° C. The addition of nitric acid to its concentrated solution precipitates a lower hydrate containing 10H2O. The hydrogen-ion concentration in a 0.05 N solution is 3.5×10-3.

A well-defined series of crystalline salts, of composition R5H4[B(W2O7)6].xH2O (R = NH4, Li, K, Na, Ag; R2 = Ba, Ca, Cd, Cu, Mg, Ni), has been obtained by careful addition of the metal hydroxide or carbonate to 12-tungstoboric acid. These salts are isomorphous with the corresponding salts of other 12-heteropoly acids; for instance, in addition to the examples already given, the sodium salt, Na5H4[B(W2O7)6].27H2O, is isomorphous with the similarly constituted sodium metatungstate, Na6H4[H2(W2O7)6].27H2O. The equivalent conductivities of solutions of the sodium salt, containing 1/5 molecule in v litres at 25° C., have been found to be:

v =32641282565121024
Λ =183.9196.0203.2213.6225.3235.3


These values correspond with those of a neutral pentabasic salt, but the neutralisation curve shows that at least two more of the hydrogen atoms are replaceable. A guanidinium salt, (CN3H6)6H3[B(W2O7)6], has been obtained, and, according to Copaux, the addition of mercurous nitrate to a solution of the sodium salt yields a crystalline precipitate of the normal mercurous salt, Hg9[B(W2O7)6].12H2O.


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