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Updated: Apr 21, 2026

Ammonia Synthesis at Low Pressure
Published on: August 23, 2017
Effect of ammonia on the volatility of organic diacids
Andrea L Paciga1, Ilona Riipinen, Spyros N Pandis
1Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Abstract:
The effect of ammonia on the partitioning of two dicarboxylic acids, oxalic (C2) and adipic (C6) is determined. Measurements by a tandem differential mobility analysis system and a thermodenuder (TD-TDMA) system are used to estimate the saturation vapor pressure and enthalpy of vaporization of ammonium oxalate and adipate. Ammonia dramatically lowered the vapor pressure of oxalic acid, by several orders of magnitude, with an estimated vapor pressure of 1.7 ± 0.8 × 10(–6) Pa at 298 K. The vapor pressure of ammonium adipate was 2.5 ± 0.8 × 10(–5) Pa at 298 K, similar to that of adipic acid. These results suggest that the dominance of oxalate in diacid concentrations measured in ambient aerosol could be attributed to the salt formation with ammonia.
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