A thermodynamic model for the description of vapor-liquid-solid equilibria is introduced. This model is a combination of the extended UNIQUAC model for electrolytes and the Soave-Redlich-Kwong cubic equation of state. The model has been applied to aqueous systems containing ammonia and/or carbon dioxide along with various salts. Model parameters valid in the temperature range 0-110 degrees C, the pressure range from 0-100 bar, and the concentration range up to approximately 80 molal ammonia are given. The model parameters were evaluated on the basis of more than 7000 experimental data points. (C) 1999 Elsevier Science Ltd. All rights reserved.