Vapour pressure
Vapour pressure at any temperature and boiling point at any pressure, with the curve on a log scale. Compare up to three compounds.
Compounds
| Compound | P at 25.0 °C | bp at 100 mbar | Normal bp |
|---|---|---|---|
| WaterAntoine, NIST WebBook, fitted 1 to 100 °C | 31.58 mbar | 45.9 °C | 100.0 °C |
| EthanolAntoine, NIST WebBook, fitted −5 to 100 °C | 78.33 mbar | 29.3 °C | 78.3 °C |
Vapour pressure curve
Solid: inside the temperature range the Antoine constants were fitted for. Thin dashed: extrapolated. Dashed: estimated from the boiling point. Dots: normal boiling points at 1 atm.
Details
- Water
- A 8.07131, B 1730.63, C 233.426log₁₀(P/mmHg) = A − B/(C + T/°C), 1 to 100 °C
- Ethanol
- A 8.20417, B 1642.89, C 230.3log₁₀(P/mmHg) = A − B/(C + T/°C), −5 to 100 °C
Where the curves come from
Compounds with Antoine constants in our database (NIST WebBook) are drawn from log10(P/mmHg) = A − B/(C + T). The solid part of the curve is the temperature range the constants were fitted for; beyond it the curve is extrapolated and drawn thin and dashed. Constants that contradict a measured boiling point of the same compound are not used.
A compound without vapour pressure data but with a boiling point on file gets an estimated curve, drawn dashed: an Antoine-form curve through the boiling point with its slope from Trouton's rule, corrected for hydrogen bonding in alcohols and water. The nomograph explains it and how well it agrees with measured data.
The normal boiling point is where the vapour pressure reaches 1 atm, 1013.25 mbar. Hover over the chart to read every curve at one temperature.
Sources
- Antoine constants: NIST Chemistry WebBook, as stored with their fitted ranges.
- Boiling points for the estimates: CAS Common Chemistry, as stored in our catalogue.