# Pressure-Temperature Nomograph Interactive Tool

Slider A is currently locked as the pivot. Slider B is currently locked as the pivot. Slider C is currently locked as the pivot.
A
Observed Boiling Point at Pressure "P" (mmHg)
B
Boiling Point Corrected
at 1 atm (760 mmHg)
C
Pressure "P" (mmHg)
1 atm = 760 mmHg

## Boiling Point vs Pressure Calculator

### To find a boiling point under a set vacuum

Chart B - Enter the known boiling point (or slide the bar) and click the lock.

Chart C - Select the pressure you are working at (Torr or mmHg) and click the lock.

### To find a corrected boiling point at 760 mmHg

Chart A - Enter the observed boiling point (or slide the bar) and click the lock.

Chart C - Select the pressure you are working at (Torr or mmHg) and click the lock.

## Estimate Boiling Point and Vapor Pressure

Use the interactive controls above to simplify calculations and improve the efficiency of your distillation or evaporation requirements.

Our Pressure-Temperature Nomograph tool is an application of the Clausius-Clapeyron equation, which assumes the heat of vaporization is a constant over a pressure range. The Antoine equation gets around this assumption by using empirical data for each unique liquid under consideration.

Give your pressure and temperature inputs in any of five units of pressure (atmospheres, bar, kilopascals, pounds per square inch, or millimeters of mercury) and five units of temperature (degrees Celsius, Kelvin, Fahrenheit, Rankine, or Réaumur).

 Clausius-Clapeyron Equation (Relation)1 Integration of the Clausius-Clapeyron Equation2 Antoine Equation3 The standard version of the Clausius-Clapeyron equation was derived by Rudolf Clausius in 1850. The relation can be written in many different derivations from the state postulate to achieve an equation for use in phase transition calculations. The relation describes the slope of a plot of temperature against pressure. The slope is equal to the change in specific entropy divided by the change in specific volume. The integration of the Clausius-Clapeyron equation is usually used for calculating the vapor pressure at a new temperature, given the current or original temperature. The ΔHvap is the enthalpy of vaporization; R is the gas constant. This integration assumes that the molar enthalpy of vaporization does not vary with temperature over the integration limits. In the Antoine Equation, P is equal to vapor pressure, and T is temperature. The Antoine parameters A, B, and C are determined independently for each vapor pressure-temperature experiment.

To make a simpler calculation between different units of pressure, use the Pressure Unit Converter.

## References

1. McQuarrie, D. A.; Simon, J. D. Mathematics for Physical Chemistry. University Science Books; 2008.
2. Goodman, J. M.; Kirby, P. D.; Haustedt, L.O. Tetrahedron Letters. 2000. 41, 9879-9882.
3. Thomson, G. W. Chemical Reviews. 1946. 38 (1), 1-29.