 An example of a negative azeotrope is hydrochloric acid at a concentration of 20.2% and 79.8% water (by mass).Hydrogen chloride boils at −84 °C and water at 100 °C, but the azeotrope boils at 110 °C, which is higher than either of its constituents.The maximum temperature at which any hydrochloric acid solution can boil is 110 °C.