Units
The coefficients of Antoine's equation are normally given in mmHg—even today where the SI is recommended and pascals are preferred. The usage of the pre-SI units has only historic reasons and originates directly from Antoine's original publication.
It is however easy to convert the parameters to different pressure and temperature units. For switching from degrees Celsius to kelvin it is sufficient to subtract 273.15 from the C parameter. For switching from millimeters of mercury to pascals it is sufficient to add the common logarithm of the factor between both units to the A parameter:
The parameters for °C and mmHg for ethanol
-
A B C 8.20417 1642.89 230.300
are converted for K and Pa to
-
A B C 10.32907 1642.89 -42.85
The first example calculation with TB = 351.47 K becomes
A similarly simple transformation can be used if the common logarithm should be exchanged by the natural logarithm. It is sufficient to multiply the A and B parameters by ln(10) = 2.302585.
The example calculation with the converted parameters (for K and Pa):
-
A B C 23.7836 3782.89 -42.85
becomes
(The small differences in the results are only caused by the used limited precision of the coefficients).
Read more about this topic: Antoine Equation
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