Enter a temperature, choose your temperature unit, plug in your Antoine constants A, B, and C, and this Antoine Equation Calculator gives you the vapor pressure of a substance in your chosen pressure unit — along with the log₁₀(pressure) and your temperature converted to Kelvin.
Vapor Pressure
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Log₁₀(Pressure)
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Temperature in Kelvin
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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.
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.
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.
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.
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.
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.
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.