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Why is (tri-)ammonium phosphate ((NH4)3PO4) so unstable?
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Paschal Ejims
Why is (tri-)ammonium phosphate ((NH4)3PO4) so unstable?
Ammonium phosphates are solids between 0 and 75°C. Because ammonium
hydroxide $(\ce{NH4OH})$ is a much weaker base than the common metal
hydroxides, ammonium phosphates are comparatively unstable. Both
triammonium phosphate ($\ce{(NH4)3PO4}$) and the double salt
($\ce{(NH4)3PO4.2(NH4)2HPO4}$) are unstable at room temperature and
evolve ammonia to form diammonium phosphate. Even the commercial mono-
and diammonium phosphates exhibit an ammonium vapor pressure in the
solid form and in solution. Although MAP is more stable than DAP, it
decomposes at high temperature to give ammonia and polyphosphoric
acid. Diammonium phosphate decomposes to give ammonia and monoammonium
phosphate at around 70°C.
Ammonium phosphates are solids between 0 and 75°C. Because ammonium hydroxide $(\ce{NH4OH})$ is a much weaker base than the common metal hydroxides, ammonium phosphates are comparatively unstable. Both triammonium phosphate ($\ce{(NH4)3PO4}$) and the double salt ($\ce{(NH4)3PO4.2(NH4)2HPO4}$) are unstable at room temperature and evolve ammonia to form diammonium phosphate. Even the commercial mono- and diammonium phosphates exhibit an ammonium vapor pressure in the solid form and in solution. Although MAP is more stable than DAP, it decomposes at high temperature to give ammonia and polyphosphoric acid. Diammonium phosphate decomposes to give ammonia and monoammonium phosphate at around 70°C.
Source: (2005) Ammonium Phosphates and Ammonium Sulfate. In: Synthetic Nitrogen Products. Springer, Boston, MA. DOI: 10.1007/0-306-48639-3_12.
Source: (2005) Ammonium Phosphates and Ammonium Sulfate. In: Synthetic Nitrogen Products. Springer, Boston, MA. DOI: 10.1007/0-306-48639-3_12.
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