The boiling point of a liquid is defined as the temperature (in K) at which the vapour pressure equals the standard atmospheric pressure 101.325 kPa. The influence of impurities on the boiling point depends greatly upon the nature of the impurity. The methods can be applied to liquid and low-melting substances, provided that they do not undergo chemical change below the boiling point.

The methods are: the ebulliometer, the dynamic method, the distillation method, the method according to Siwoloboff, the photocell detection, the differential thermal analysis, the differential scanning calorimetry. The photocell detection and thermal analysis permit the determination of boiling as well as melting temperatures. The dynamic method has the advantage that it can also be applied to the determination of the vapour pressure.

OECD (1995), Test No. 103: Boiling Point, OECD Guidelines for the Testing of Chemicals, Section 1, OECD Publishing, Paris, https://doi.org/10.1787/9789264069541-en.