Below enter the
pressure of known
boiling point
Below enter the
boiling point under
this pressure
Above enter
a pressure
to calculate the
boiling point
or above enter
a boiling point
to calculate
the pressure
heat of
equals about
  • Any pressure unit can be used. The result
    will be displayed in the same units.
  • The results are only roughly evaluated and
    can sometimes differ a bit from their real values.
  • Initially the calculator is set to evaluate results for
    water and substances of similar heat of
    evaporation (DMF, aniline, toluene)
Below enter
pressure for
a known
boiling point
Below enter the
boiling point under
this pressure
Above enter another
pressure of known
boiling point
   Above enter the
boiling point under
the other pressure
  • Pressure unit must be identical for both values
ether, hexanes, carbon disulfide,
methylene chloride
acetone, benzene, acetonitrile,
bromine, chloroform, cyclohexane,
ethyl acetate, triethylamine
dioxane, methanol, ethanol
nitric acid, nitromethane
pyridine, phosphorous oxychloride
water, butanoles, propanoles
aniline, toluene, bromoform
DMSO, nitrobenzene, octanoles,
sulfuric acid
mercury, formamide, glycol
high molecular or high
boiling compounds

Using the Calculator

Suppose you are going to perform distillation under reduced pressure. You know that your substance boils at 89°C under pressure of 1 Torr. Unfortunately your pump cannot go that low. It can only achieve 5 Torrs of vacuum. What will be the boiling point of your compound under this pressure? The calculator can help. Generally three cases can be distinguished:

1. You know only one value of boiling point for your substance. In this case just fill the two upper fields with the values you know. You can now roughly evaluate its boiling point. Take water for example. Enter 760 (millimeters of mercury, or 1013 hPa -- units do not matter) as the pressure value and 100 as the boiling point. Now you can calculate its boiling point under any pressure. Type 15 in the second left field and 18 will appear in the second right field. This is the answer. Water boils at 18°C under 15 millimeters of mercury. Simple, isn`t it? You can do reverse calculation, too. You want to know what pressure is needed to make water boil at 50°C. Type 50 in the second right field and the result (89) will be displayed.

2. If you know the heat of evaporation of your substance you can enter it in the appropriate field. This should help to obtain more exact results. If you do not know the heat of evaporation, press the CHOOSE button and try to select your (or similar) compound from the list.

3. You know at least two boiling points under two different pressure values. You can sometimes find them in a journal or in tables. You are lucky then. Press the CALIBRATION button and fill in the form. The heat of evaporation of your substance will be calculated when you ACCEPT these data. This means you can obtain very accurate results now. Take crotonic acid for example: It boils at 185°C under 760 mmHg (atmospheric pressure) and at 80°C under 10 mmHg. Enter these data into calibration form and accept them. The heat of evaporation will be calculated and displayed (55.5 kJ/mol). You can evaluate the boiling point of crotonic acid quite accurately now.

Home Page

ADVAMACS.COM - Advanced building blocks