**Who is Antoine, and why did he think it important that the Clausius-Clapeyron equation be modified?**

melonie lewis 7/27/99-

Chemists often use the Clausius-Clapeyron equation to estimate the vapor pressures of pure liquids or solids. Several of the assumptions made in the derivation of the equation fail at high pressure and near the critical point, and under those conditions the Clausius-Clapeyron equation will give inaccurate results. Chemists still like to use the equation because it's good enough in most applications and because it's easy to derive and justify theoretically.**Vocabulary**Antoine equation

Clausius-Clapeyron equation

enthalpy of sublimation

enthalpy of vaporization

ideal gas law constant

vapor pressureChemical engineers sometimes need more more reliable vapor pressure estimates. The

*Antoine equation*is a simple 3-parameter fit to experimental vapor pressures measured over a restricted temperature range:log P = A - __B__

T + CAntoine coefficients for many substances are tabulated in

*Lange's Handbook of Chemistry*(12th ed., McGraw-Hill, New York, 1979) and they are available online from NIST's Chemistry WebBook. The following books, CD's, and Web sites give parameters and further information about the Antoine equation:**Antoine Coefficient Conversion Calculator**(Process Data Control Corporation) A Java applet that converts Antoine coefficients from one system of units to another.

http://www.pdccorp.com/java/conversion.html (7/27/99)**Antoine Equation**(nextstep@athena.compulink.gr) A JavaScript calculator that estimates vapor pressure for a few common materials using the Antoine equation.

http://www.compulink.gr/users/nextstep/antoine.html (4/11/99)**Properties of Gases and Liquids**(R. C. Reid, J. M. Praunitz, B. E. Poling) This handbook provides models and parameters for estimating thermodynamic properties of gases and liquids, both pure and mixtures, including enthalpies, entropies, fugacity coefficients, heat capacities, and critical points; vapor-liquid and liquid-liquid equilibria. ISBN: 0070517991, published by McGraw-Hill.

http://www.amazon.com/exec/obidos/ISBN%3D0070517991/002-3780039-4315040 (4/11/99)**Vapor Pressures of Pure Substances**(Bernhard Spang) A brief introduction to the Antoine equation, used to estimate the vapor pressure of substances as a function of temperature. Includes Antoine equation parameters for selected substances.

http://chemengineer.about.com/library/weekly/aa071497.htm (4/11/99)

General Chemistry Online! What is the Antoine equation?Copyright © 1997-2010 by Fred Senese

Comments & questions to fsenese@frostburg.edu

Last Revised 08/17/15.URL: http://antoine.frostburg.edu/chem/senese/101/liquids/faq/print-antoine-vapor-pressure.shtml