Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Study of Azeotrope Phase Equilibrium with the Advanced Distillation Curve Approach



Amelia Hadler, Lisa S. Ott, Thomas J. Bruno


Azeotrope mixtures are among the most fascinating, and at the same time the most complicated manifestations of phase equilibrium.  They are also a critical aspect of many industrial processes and products.  Indeed, with the current interest in alcohol based befouls and extended fuels, the need to deal with azeotrope is at the forefront.  Dealing with mixtures of hydrocarbons with lower alcohols means dealing with azeotropes.  Classical methods for the study of complex fluid behavior include static and dynamic equilibrium cells that include vapor and liquid recirculation.  These are complex , costly apparatus that require highly trained operators, usually months of labor intensive work per mixture, and the data analysis is also rather complex.  Simpler approaches to the fundamental study of azeotropes are highly desirable, even if they provide only selected cuts through the phase diagram.  Recently, we have introduced an advanced distillation curve measurement method featuring (1) a composition explicit data channel for each distillate fraction (for both qualitative and quantitative analysis), (2) temperature measurements that are true thermodynamic state points that can be modeled with an equation of state, (3) temperature, volume and pressure measurements of low uncertainty suitable for equation of state development, (4) consistency with a century of historical data, (5) an assessment of the energy content of each distillate fraction, (6) trace chemical analysis of each distillate fraction, and (7) corrosivity assessment of each distillate fraction.  For the phase diagram of an azeotrope, this method provides the bubble point temperature and dew point composition.  In this paper, we present the application of the approach to several simple azeotropic mixtures: ethanol + benzene and dioxane + water.
Fluid Phase Equilibria


advanced distillation curve, azeotrope, phase equilibrium, benzene, ethanol, dioxane, water


Hadler, A. , Ott, L. and Bruno, T. (2009), Study of Azeotrope Phase Equilibrium with the Advanced Distillation Curve Approach, Fluid Phase Equilibria, [online], (Accessed May 26, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created July 14, 2009, Updated October 12, 2021