Antoine Equation Calculator

Antoine Equation Calculator

The Antoine equation is a mathematical expression used to describe the relation between the vapor pressure and temperature for pure components. Use this calculator to find the vapor pressure ($P$) based on temperature ($T$).

Vapor Pressure (P) 0.00 mmHg

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Understanding the Antoine Equation

The Antoine equation is a semi-empirical correlation that relates the saturation vapor pressure of a liquid to the temperature. It is widely used in chemical engineering and thermodynamics to predict phase behavior. The standard form of the equation used in this calculator is:

log₁₀(P) = A – [B / (T + C)]

Where:

• P: Vapor Pressure (usually in mmHg)
• T: Temperature (usually in °C)
• A, B, C: Substance-specific constants

Common Substance Constants (Water, Ethanol, Acetone)

To use the calculator effectively, you need the correct coefficients for your specific chemical. Here are some common examples for the temperature range where water is liquid:

Substance	A	B	C
Water (H2O)	8.07131	1730.63	233.426
Ethanol	8.04494	1554.3	222.65
Acetone	7.02447	1161.0	224.0

Example Calculation

If you want to find the vapor pressure of Water at 100°C:

1. Input A = 8.07131, B = 1730.63, C = 233.426.
2. Input Temperature T = 100.
3. The formula calculates: log₁₀(P) = 8.07131 – [1730.63 / (100 + 233.426)].
4. log₁₀(P) ≈ 2.8808.
5. P = 10^2.8808 ≈ 760 mmHg (Standard Atmospheric Pressure).

Frequently Asked Questions

Can I use Kelvin?
Most Antoine constants published in literature (like the NIST Chemistry WebBook) are specifically calibrated for either Celsius or Kelvin. This calculator uses the Celsius standard. If your constants are for Kelvin, ensure you convert the temperature input accordingly.

Why is my result different from observed data?
The Antoine equation is an approximation. Each set of constants (A, B, C) is valid only for a specific temperature range. Using constants outside their specified range will lead to inaccurate results.

function calculateVaporPressure() { var a = parseFloat(document.getElementById('antoineA').value); var b = parseFloat(document.getElementById('antoineB').value); var c = parseFloat(document.getElementById('antoineC').value); var t = parseFloat(document.getElementById('temperatureT').value); var resultDiv = document.getElementById('antoineResult'); var pressureSpan = document.getElementById('pressureOutput'); if (isNaN(a) || isNaN(b) || isNaN(c) || isNaN(t)) { alert("Please enter valid numeric values for all fields."); return; } // Temperature safety check to prevent division by zero if (t + c === 0) { alert("Error: T + C cannot equal zero (Division by zero)."); return; } // Standard Antoine Equation: log10(P) = A – (B / (T + C)) var log10P = a – (b / (t + c)); var p = Math.pow(10, log10P); pressureSpan.innerText = p.toLocaleString(undefined, { minimumFractionDigits: 2, maximumFractionDigits: 4 }); resultDiv.style.display = 'block'; // Scroll to result on small screens if(window.innerWidth < 600) { resultDiv.scrollIntoView({ behavior: 'smooth' }); } }