Preparing ammonium hexafluorozirconate
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Ammonium hexafluorozirconate - (NH4)2ZrF6 - is prepared by dissolving freshly precipitated Zr(OH)4 in concentrated ammonium bifluoride - NH4HF2 in a polypropylene beaker. A 10 % excess of ammonium bifluoride is used:
Zr(OH)4(s) + 3 NH4HF2(aq) === > (NH4)2ZrF6(aq) + NH3(aq) + 4 H2O(l)
The reaction is accompanied with heat generation. Gently simmer the solution on steam bath to obtain full dissolution. If the solution is still turbid, hot-filter to clarity.
On cooling and chilling overnight, well-formed crystals of ammonium hexafluorozirconate are obtained.
Pyrolysis of ammonium hexafluorozirconate yields zirconium tetrafluoride:
(NH4)2ZrF6(s) === > ZrF4(s) + 2 NH4F(g)
