Antoine Equation Calculator

The Antoine Equation is a three-parameter formula used in chemistry and engineering to estimate the vapor pressure of a pure liquid at a given temperature — useful for distillation design, safety analysis, and thermodynamic modeling. Enter a temperature and your Antoine constants A, B, and C into the Antoine Equation Calculator, then select your preferred pressure unit to get the calculated vapor pressure. Secondary outputs include the log₁₀ of the pressure and the input temperature converted to Kelvin.

°C

Temperature at which to calculate vapor pressure

Antoine constant A (dimensionless)

Antoine constant B (temperature units)

Antoine constant C (temperature units)

Results

Vapor Pressure

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Log₁₀(Pressure)

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Temperature in Kelvin

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Frequently Asked Questions

What is the Antoine equation used for?

The Antoine equation is used to calculate the vapor pressure of a pure substance at different temperatures. It helps engineers and scientists predict when a liquid will start to boil or condense under various conditions.

What is the difference between Clausius-Clapeyron and Antoine equation?

The Clausius-Clapeyron equation is a theoretical formula that shows how vapor pressure changes with temperature using basic thermodynamic properties. The Antoine equation is an empirical formula with substance-specific constants that provides more accurate results for practical calculations.

How do I find Antoine constants A, B, and C for different substances?

Antoine constants are experimentally determined values specific to each substance. They can be found in chemical engineering handbooks, NIST databases, or scientific literature. Common substances like water, ethanol, and benzene have well-documented constants.

What temperature range is valid for Antoine equation calculations?

The Antoine equation is typically valid over specific temperature ranges for each substance, usually between the melting point and critical temperature. Using the equation outside these ranges may give inaccurate results.

Why is vapor pressure calculation important?

Vapor pressure calculations are crucial for designing distillation columns, determining boiling points at different pressures, safety assessments for volatile substances, and understanding phase equilibrium in chemical processes.

Can the Antoine equation be used for mixtures?

The Antoine equation applies to pure substances only. For mixtures, you need to use modified equations like Raoult's law combined with Antoine equations for each component, or more complex equations of state.

What units should I use for temperature in the Antoine equation?

The temperature units depend on how the Antoine constants were determined. Most commonly, temperature is in Celsius for the standard form log₁₀(P) = A - B/(C + T), but some versions use Kelvin. Always check the source of your constants.