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Vapor Pressure (Antoine) Calculator Documentation

Note: This documentation is based on the standard Antoine equation for vapor pressure correlation.

1. Objective

The Vapor Pressure Antoine Calculator is a simple tool to estimate the vapor pressure of a pure component at a given temperature using the Antoine equation.

2. Design Basis & Methodology

The calculator uses the Antoine equation, a widely used semi-empirical correlation that describes the relationship between vapor pressure and temperature.

Key Formula:

log10(P) = A - (B / (C + T))

Where:

  • P: Vapor pressure.
  • T: Temperature.
  • A, B, C: Component-specific constants, known as Antoine coefficients.

The units of P and T depend on the source of the constants (e.g., P in mmHg, T in °C).

3. Input Parameters

  • Antoine Coefficients (A, B, C): These are empirical constants specific to each chemical substance and a specific temperature range.
  • Temperature (T): The temperature at which to calculate the vapor pressure.

4. Output Results

  • Vapor Pressure (P): The calculated vapor pressure of the substance at the given temperature.

5. Limitations and Assumptions

  • The Antoine equation is only accurate over a limited temperature range for which the constants were derived.
  • The accuracy is entirely dependent on the quality of the Antoine coefficients used.
  • The equation applies to pure components only. It cannot be used directly for mixtures.

6. Example Calculation

Goal: Calculate the vapor pressure of water at its normal boiling point (100°C).

Given:

  • Substance: Water
  • Antoine Coefficients (for P in mmHg, T in °C):
    • A = 8.07131
    • B = 1730.63
    • C = 233.426
  • Temperature (T): 100 °C

Calculation: log10(P) = A - (B / (C + T)) log10(P) = 8.07131 - (1730.63 / (233.426 + 100)) log10(P) = 8.07131 - (1730.63 / 333.426) = 8.07131 - 5.1905 = 2.8808 P = 10^2.8808 ≈ 760 mmHg

Result: The calculated vapor pressure is 760 mmHg, which is equal to 1 standard atmosphere, as expected.

Reference Standards

  • NIST Chemistry WebBook: Antoine Equation Parameters database.
  • Reid, R.C., Prausnitz, J.M., Poling, B.E.: The Properties of Gases and Liquids.
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