Mixtures of alkali nitrates in water have good potential to be used as working fluids in absorption refrigeration systems. In this study the extended version of the Brunauer, Emmett, and Teller (BET) model has been used to predict the saturation temperature and vapor pressure of LiNO3-KNO3-NaNO (3)/H2O mixtures with two salt ratio values (53:28:19 and 53:42:05). The parameters of the model were obtained from the literature, with the exception of the equilibrium constant of potassium nitrate, which was obtained from solubility data of the KNO3/H O-2 system. The results were in good agreement with the experimental data reported in the literature. Using the concept of the supersaturation index, the model also predicted the salt present in the solid phase in the solid-liquid equilibrium. To validate the predictive capacity of the model, an experimental study of the crystallization of the solutions at temperatures of 325.15 and 335.15 K was conducted. The results obtained proved to be in good agreement with predictions. Finally, the information obtained was used to construct the Duhring diagram, which is very important for the design and simulation of the thermodynamic cycles of absorption refrigeration systems.