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Liquid and vapour enthalpies and saturated vapour pressure correlations were developed using the Chebychev series approach to curve fitting for the liquid and vapour phases of NH3–H2O(ammonia-water) solutions using experimental data. The average percentage deviations of the compared values were significantly low (±0.73925 for the liquid phase enthalpies, ±1.596 for the vapour phase enthalpies and ±0.513 for saturated vapour pressures). Therefore, the correlations derived can be used to calculate the Liquid and vapour enthalpies of NH3–H2O solution. Furthermore, data generated for the two phases were compared with values generated from the commonly used models of Patek and Klomfar (1995). While data generated for the liquid phase enthalpies were comparable for the two procedures (±0.08805 percentage deviation), the same conclusion could not be reached for the vapour phase as the deviation of calculated enthalpies from the model developed in this work increased with an increase in temperature. Since the generation and comparison of vapour enthalpies requires saturated vapour pressure values of the NH3–H2O solution, the paper has inadvertently provided a corresponding procedure and correlations for calculating this property. The paper further identified temperature and NH3–H2O concentration ranges that generate reliable enthalpies values for the three properties.