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Ammonia Volatilization Reaction Mechanism Between Ammonium Sulfate and Carbonate Systems

Feagley, S. E., Hossner, L. R.
Soil Science Society of America journal 1978 v.42 no.2 pp. 364-367
ammonia, ammonium carbonate, ammonium sulfate, barium carbonate, calcium carbonate, carbon dioxide, gases, magnesium carbonate, pH, reaction mechanisms, silt loam soils, volatilization
The mechanism by which NH₃ is lost in the reaction between (NH₄)₂ SO₄ and CaCO₃, BaCO₃, MgCO₃, and a calcareous Norwood silt loam soil was investigated. Results obtained in the laboratory indicated that the reaction proceeded through an NH₄HCO₃ intermediate. The ratio of NH₃ to CO₂ volatilized approached a 2:1 ratio of NH₃/CO₂ gases for the first 2 to 6 hours of the reaction. It then decreased to an apparent equilibrium ratio of 1:1 for the remainder of the 96-hour reaction period. The pH of the reaction interface between (NH₄)₂SO₄ surface applied to CaCO₃ was never > 8.4. These data indicate that at no point was there a high enough pH to form (NH₄)₂CO₃. Thus, if any solid formed it would be NH₄HCO₃ and not (NH₄)₂CO₃.