ENTHALPY CHANGES UPON PARTIAL EVAPORATION OF AQUEOUS-SOLUTIONS CONTAINING AMMONIA AND CARBON-DIOXIDE

The enthalpy changes upon partial evaporation of aqueous solutions con taining ammonia and of aqueous solutions containing ammonia and carbon dioxide were measured at temperatures from 313 to 393 K with a thin f ilm evaporator flow calorimeter. The molalities of ammonia and carbon dioxide entering the calorimeter ranged up to 12 and 6 mol/kg, respect ively. The physicochemical model originally developed by Edwards et al . (1978) and further modified and extended by Kurz et al. (1995) to de scribe phase equilibria in aqueous systems containing ammonia and carb on dioxide is used to derive a predictive enthalpy model for this comp lex, chemical reactive system. Comparisons between the new experimenta l results for the enthalpy change upon partial evaporation and model p redictions reveal deviations mostly within the experimental uncertaint ies.