 Ethanol boils at 78.4 °C, water boils at 100 °C, but the azeotrope boils at 78.2 °C, which is lower than either of its constituents.Indeed, 78.2 °C is the minimum temperature at which any ethanol/water solution can boil at atmospheric pressure.In general, a positive azeotrope boils at a lower temperature than any other ratio of its constituents.