The Antoine Equation and Other Data-Fitting Equations

6 THE ANTOINE EQUATION AND OTHER DATA-FITTING EQUATIONS 

To be mathematically precise, we would write of the logarithm as log (p/torr) and write B and C as B, °C and C, °C. That would make it unnecessary to state with the equation what units of p and T are used. While this is mathematically precise, it is almost never done. The constants are almost always presented as in Table A.2, and it is assumed that the user is not terribly upset about taking the dimensionless log of a quantity that is not itself dimensionless. 

Inserting the values of the constants for water from Table A.2, and the value of 1.00 atm expressed in torr we find 

This does not prove the overall accuracy of the Antoine equation, but does show that whoever fitted the constants to the experimental data for water made them represent the NB P (100°C) very well.  

There seems to be widespread agreement that the Antoine equation is the best three- constant vapor-pressure equation it is very widely used. But now that our computers have grown so large and powerful, we can easily use more complex equations. 

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