Atomistry » Molybdenum » Compounds » Ammonium Octamolybdate
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Ammonium Octamolybdate, (NH4)2Mo8O25.16H2O

Ammonium Octamolybdate, (NH4)2Mo8O25.16H2O, has been described, but may be regarded as ammonium trihydrogen tetra-molybdate, NH4O.(OH)2MoO(O.MoO2)3.OH.5H2O. This, if left in a vacuum over sulphuric acid, loses 5H2O, and a further molecule of water when heated to 160° C. Its aqueous solution at 40° C. yields crystalline needles of the trihydrogen pentamolybdate NH4O.(OH)2MoO(O.MoO2)4.OH. Hexa-, hepta-, nona- undeca-, dodeca-, and trideca-molybdates have also been prepared.

The compound NH3.MoO2.(MoO3)2.5H2O is described as an unstable brown crystalline substance obtained on mixing an aqueous solution of ordinary ammonium molybdate with a solution of molybdenum dioxide in hydrochloric acid.

The double salts NaNH4Mo3O10.H2O, 2Na2O.7(NH4)2O.21MoO3.15H2O, and 3Na2O.7(NH4)2O.25MoO3.30H2O have been described.


Three compounds have been described: NH4IO3.MoO3.H2O; (I2O5.2MoO3)4.3(NH4)2O.6H2O; I2O5.2MoO3.(NH4)2O.H2O; as well as the periodo molybdates, (NH4)5IO6.6MoO3.6H2O and (NH4)HIO6.4MoO3.
Complex molybdates of ammonium, of the types (NH4)3H6[R•••(MoO4)6]7H2O, where R••• is Fe, Cr, or Al, and (NH4)3H7[R••(MoO4)6].xH2O, where R•• is Co, Mn, or Mg, have been prepared, as also have ammonium rare-earth-molybdates and a nicotine ammonium molybdate. The existence has been recorded of double salts of the following formulae: (NH4)2Cu(MoO4)2.2NH3; CuMoO4.2NH3.H2O; (NH4)2Cd(MoO4)2.2NH3; (NH4)2Ni(MoO4)2.2NH3; (NH4)2Co(MoO4)2. 2NH3; and 3(NH4)2MoO4.CO2(MoO4)3.4MoO3.10H2O.
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