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

Ammonium Tungstates






The normal salt cannot be obtained by dissolving tungstic acid in aqueous ammonia, since on concentration ammonia is lost and an acid salt remains. That the normal tungstate is present in solution would appear evident from the fact that calcium chloride precipitates the normal calcium tungstate. It may be obtained as a white mass by the addition of hydrated tungstic acid to liquid ammonia. The normal tungstate is very soluble in water and readily loses ammonia.

The acid tungstate, 2(NH4)2O.3WO3.3H2O, sometimes crystallises from a very concentrated neutral solution of tungstic acid in ammonia, which, however, more often yields the paratungstate. The crystals, which are warty and indistinct, give off ammonia in contact with the air, leaving the paratungstate.

Ammonium paratungstate, 5(NH4)2O.12WO3.11H2O, is the product most frequently obtained by the interaction of tungstic acid and ammonia; for example, when tungstic acid is dissolved in aqueous ammonia, or when ammonia is added to a solution of ammonium meta- tungstate, on concentration of the resulting solution the paratungstate crystallises out. It is dimorphous and yields both acicular needles and laminated plates. The former are the more stable and are pseudo-rhombic (a:b:c = 0.7995:1:0.4582). The plates are triclinic pinacoidal, a:b:c = 0.9785:1:1.2154; α = 65° 47', β = 117° 33', γ = 119° 2'. Both forms are stable at ordinary temperatures, but when heated, begin to lose ammonia at 60° C.; at 100° C. lose 7 molecules of water; and at 250° C. yield the glass-like colloidal tungstate (see below). If the crystals are heated in contact with dry ammonia, they lose water and absorb ammonia. When boiled in aqueous solution for several days, the metatungstate is formed.

This salt was regarded by Berzelius and Anthon as the ditungstate; Lotz and Scheibler formulated it as 3(NH4)2O.7WO3.6H2O, but the formula given above is due to Marignac. Rosenheim suggests (NH4)10H4[H4(WO4)6(W2O7)3].7H2O.

The hydrate, 5(NH4)2O.12WO3.5H2O or 3(NH4)2O.7WO3.3H2O, is obtained by evaporation of a solution of ammonium paratungstate at temperatures near the boiling-point. It yields small, glistening, monoclinic prisms,

a:b:c = 1.0442:1:0.7871; β = 109° 50'.

On heating at 100° C. it loses 2 molecules of water. The electrical conductivity of solutions of this salt has been investigated. At 25° C. the equivalent conductivity of a N/128 solution increased from 95.1 to 109.0 reciprocal ohms in six days. The rate of increase was greater when the temperature was raised and was complete in about three hours at 80° C. The following table shows the equivalent conductivities at 25° C. of solutions containing 1/10 of a molecular weight in v litres, (a) when freshly made, (b) after heating at 80° C. for three hours and then allowing to cool:

v =32641282565121024
(a)Λ =62.071.783.793.3103.9120.2
(b)Λ =102112121131139148


A hydrate, 5(NH4)2O.12WO3.6H2O, has been obtained by the addition of acetic acid to a solution of ammonium tungstate.

The acid salt, 2(NH4)2O.5WO3.5H2O, is produced by cooling a hot saturated solution of ammonium paratungstate, when it separates in small octahedral plates with crystallographic elements:

a:b:c = 1.1204:1:1.7190; α = 105° 46', β = 95° 17', γ = 90° 1'.

It dissolves in 26 to 29 parts of water. On heating at 100° C. it loses about seven-tenths of its water of crystallisation.

The octatungstate, 3(NH4)2O.8WO3.8H2O, is sometimes obtained when a solution of the preceding salt is allowed to crystallise; but from a hot solution, the trihydrate, 2(NH4)2O.5WO3.3H2O, has been obtained.

A colloidal tungstate, of composition (NH4)2O.6WO3.4 or 6H2O, results as a vitreous mass when ammonium para- or meta-tungstate is heated to 250° C. It is miscible with water in all proportions and absorbs ammonia readily, thus reverting to the meta-salt.

The following double ammonium sodium tungstates have been prepared: 3(NH4)2O.3Na2O.16WO3.22H2O; 16(NH4)2O.4Na2O.50WO3.50H2O; 6(NH4)2O.5Na2O.24WO3.27H2O.

The compound, WO3.3NH3, probably ammonium imidotungstate, NH:WO(O.NH4)2, is obtained by heating the oxychloride, WO2Cl2, with liquid ammonia under pressure.

A tungstate of hydroxylamine, 4NH2OH.3WO3.3H2O, is produced when hydroxylamine hydrochloride is added to a solution of sodium tungstate; it appears as a white precipitate which turns pale yellow on drying.

Hydroxylamine ammonium tungstate, NH4O.WO4.NH4, is prepared by treating finely powdered sodium paratungstate with an aqueous solution of hydroxylamine hydrochloride, and then dissolving the product in 15 per cent, ammonia. It crystallises in black tablets on evaporating the solution over potassium hydroxide. It is a strong reducer, and immediately reduces ammoniacal silver nitrate and Fehling's solution.

The following ammonio-tungstates have been described:

Ag2WO4.4NH3;
CuWO4.2NH3.H2O;
CuWO4.4NH3;
CuO.4WO3.6NH3.8H2O;
ZnWO4.4NH3.3H2O.


© Copyright 2008-2012 by atomistry.com