Vapour pressure measurements and predictions for alcohol–gasoline blends

A simple method to successfully predict vapour-pressures of gasoline–alcohol mixtures is demonstrated. Vapour-pressures of mixtures of gasoline with methanol, ethanol, isopropanol, and t-butanol were measured at 37.8°C (100°F) as a function of mixture composition. Infinite dilution activity coefficients were found from this data and used to find constants in the Wilson equation, which predicted the vapour-pressure curves very accurately. For all systems, the vapour pressure of the gasoline was initially elevated by the addition of the alcohols, then lowered as the proportion of alcohol was increased. This shows that these solutions can be treated as pseudobinary solutions for prediction purposes.