azeotrope

1. (physics) A mixture of two or more substances whose liquid and gaseous forms have the same composition (at a certain pressure); the substances cannot be separated by normal distillation.Examples: "The formation of azeotropes due to deviations from Raoult's law was discussed in Section 1.3. An azeotrope is a mixture that, at a given pressure (the azeotropic pressure), boils at a constant temperature (the azeotropic temperature), and has the same composition (the azeotropic composition) in the equilibrium vapor and liquid phases. Homogeneous azeotropes are those that form one liquid phase at equilibrium with the vapor; heterogeneous azeotropes are those that form two liquid phases at equilibrium with each other and the vapor."; "When a ternary azeotrope does exist, the curves intersect at the same point. The presence of a unitary azeotrope curve is not a prerequisite for the generation of a ternary azeotrope."; "As the boiling point of HCl–H₂O azeotrope is lower than that of azeotrope (HNO₃–H₂O), hydrochloric acid can be eliminated efficiently by successive evaporations with nitric acid."