The atmospheric pressure can be estimated if the altitude is known. If the boiling temperature for a liquid under standard pressure is known, then the boiling point at the altitude can be estimated.
Atmospheric Pressure from Altitude
As discussed in the Chapter on Environmental Health, the atmospheric pressure at a given altitude can be estimated as:
barometric pressure in mm Hg =
= 760 * ((1 - (0.000006873 * (altitude in feet above sea level))) ^ 5.256)
Calculating the Boiling Temperature at Given Pressure
2.8808 - LOG10(atmospheric pressure in mm Hg at given altitude) =
= A / B
A =
= (entropy of vaporization at 760 mm Hg) * ((boiling temperature in °C under standard pressure) - (boiling temperature in °C at altitude))
B =
= (273.1 + (boiling temperature in °C at altitude)) - (0.15 * ((boiling temperature in °C under standard pressure) - (boiling temperature in °C at altitude)))
where:
• The entropy of vaporization for the liquid can be estimated as in the first subsection above.
• 2.8808 = LOG10(760 mm Hg)
• 273.1 °K = 0° C
If this is rearranged:
boiling temperature in °C at altitude =
= C / D
C =
= (-273.1 * (2.8808 - LOG10(atmospheric pressure in mm Hg))) + (0.15 * (2.8808 - LOG10(atmospheric pressure in mm Hg)) * (boiling temperature in °C under standard pressure)) + ((entropy of vaporization at 760 mm Hg) * (boiling temperature in °C under standard pressure))
D =
= (entropy of vaporization at 760 mm Hg) + (1.15 * (2.8808 - LOG10(atmospheric pressure in mm Hg)))
