<Dd> ln (\ displaystyle \ ln) is the natural logarithm . </Dd> <P> Saturation pressure is the pressure for a corresponding saturation temperature at which a liquid boils into its vapor phase . Saturation pressure and saturation temperature have a direct relationship: as saturation pressure is increased, so is saturation temperature . </P> <P> If the temperature in a system remains constant (an isothermal system), vapor at saturation pressure and temperature will begin to condense into its liquid phase as the system pressure is increased . Similarly, a liquid at saturation pressure and temperature will tend to flash into its vapor phase as system pressure is decreased . </P> <P> There are two conventions regarding the standard boiling point of water: The normal boiling point is 99.97 ° C (211.9 ° F) at a pressure of 1 atm (i.e., 101.325 kPa). The IUPAC recommended standard boiling point of water at a standard pressure of 100 kPa (1 bar) is 99.61 ° C (211.3 ° F). For comparison, on top of Mount Everest, at 8,848 m (29,029 ft) elevation, the pressure is about 34 kPa (255 Torr) and the boiling point of water is 71 ° C (160 ° F). The Celsius temperature scale was defined until 1954 by two points: 0 ° C being defined by the water freezing point and 100 ° C being defined by the water boiling point at standard atmospheric pressure . </P>

What's the boiling point of water in a vacuum