A Water–Urea–Ammonium Sulfamate system: Experimental investigation and thermodynamic modelling

• Thermodynamic model of the H2O(NH2)2CONH4SO3NH2 system was proposed.
• Reassessment of the H2O–(NH2)2CO was performed.
• Phase diagrams of the (NH2)2CONH4SO3NH2 and H2ONH4SO3NH2 were obtained by DSC.
• Saturated vapor pressures of the Ammonium Sulfamate aqueous solutions were determined.
• Saturated vapor pressures of the H2O(NH2)2CONH4SO3NH2 solutions were determined.

The Water–Urea–Ammonium Sulfamate ternary system was investigated by means of experimental methods and thermodynamic modelling. Experimental part of the work includes (i) DSC measurements of liquidus and solidus of the Urea–Ammonium Sulfamate, the Water–Ammonium Sulfamate subsystems with the estimation of eutectic point position and a set of experiments on the phase boundaries in the ternary system; (ii) vapor pressure measurements in the binary Water–Ammonium Sulfamate and ternary Water–Ammonium Sulfamate–Urea systems at 298.15 K in a wide concentration range. Excess Gibbs energies of the Water–Ammonium Sulfamate–Urea system and its binary subsystems were described by the Pitzer-Simonson-Clegg model which is reduced to polynomial formalism in case of nonelectrolyte systems. Results of the Water–Urea subsystem reassessment are given.

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