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Unformatted text preview: DEPENDENCE OF BOILING POINT ON PRESSURE The normal boiling point of a liquid is defined as the tempera- ture at which the vapor pressure reaches standard atmospheric pressure, 101.325 kPa. The change in boiling point with pressure may be calculated from the representation of the vapor pressure by the Antoine Equation, ln p = A 1 A 2 /( T + A 3 ) where p is the vapor pressure, T the absolute temperature, and A 1 , A 2 , and A 3 are constants. This table, which has been calculated us- ing the Antoine constants in Reference 1, gives values of t / p for a number of liquids, in units of both C/kPa and C/mmHg. The correction to the boiling point is generally accurate to 0.1 to 0.2 C as long as the pressure is within 10% of standard atmospheric pressure. A slightly less accurate estimate of t / p may be obtained from the Clausius-Clapeyron equation, with the assumption that the change in volume upon vaporization equals the ideal-gas volume of the vapor. This leads to the equationof the vapor....
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- Fall '08