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

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