| Summary: | Vapour-liquid equilibrium data for the ethanol-water system were obtained at 70, 80, 90, 100, 150, 300 and 500 mm Hg absolute pressure. No azeotrope was detected at 70 and 80 mm Hg. Azeotropic data were estimated at other experimental pressures. The VLE data were obtained using a modified Othmer still. A computerised and automatic pressure control system was integrated into the still. An effective Cottrell pump and a new vacuum sampling technique were also incorporated. The data were successfully tested for thermodynamic consistency and thereafter correlated with the NRTL, the Wilson and expansions of the Margules and van Laar equations. The two-parameter Margules and the Wilson equations gave poor correlations. The two-parameter van Laar equation gave relatively good performance. The NRTL and the four-parameter Margules equations gave performances comparable with those of the van Laar equations. After observing the failure of the above equations to predict the correct azeotropic composition, two azeotrope-embedded equations based on the four-parameter Margules and van Laar equations were proposed and tried. Vapour pressure data for ethanol and for water containing between 0 and 0.113 mole fraction potassium acetate were obtained and correlated with the Antoine equation. The effect of potassium acetate on the VLE of the ethanol-water system was studied. Data at 0.053, 0.072, 0.097 and 0.113 mole fraction potassium acetate were obtained. These salt concentrations broke the azeotrope and significantly enhanced the VLE. Minima were observed in the temperature-composition data above 0.8 mole fraction ethanol. The experimental vapour pressure data were used in the correlation of the ternary VLE data using the special binary approach. The correlation was good at low ethanol and salt concentrations but deteriorated at high ethanol concentrations.
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