Boiling Point and the Standard-State Pressure

In these tables, the defined pressure for the standard state is 1 bar (100 000 Pa). As stated by lUPAC, the present recommended change in the standard-state pressure carries no implication for standard pressures used in other contexts, e.g., the convention that normal boiling points refer to a pressure of 1 atm (101 325 Pa). Instances may occur where it is desirable to adopt yet other values forand so all authors must clearly state the value adopted. 

The phrase boiling point must be used carefully for other reasons. Care must be exercised such that the boiling process is indeed defined. Two examples which illustrate this point are MgO and LiF. Magnesium oxide does not vaporize congruently (so that the total vapor pressure depends on the ambient oxygen potential), whereas LiF vaporizes congruently but monomer, dimer, and trimer species exist in the vapor. 

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