I am really pleased that Jonathan Mitschele has taken the trouble to carry out this analysis. His observations emphasise the complexity of the situation, and most importantly that the attractive forces within the liquid are certainly not gravitational in nature.

As Ron Rich has so often pointed out, it is the polarizability of the species, in particular of the electron clouds of the exposed atoms, that dictates the boiling point (1).

However, the behavior of the series CH₄, CH₃F, CH₂F₂, CHF₃, CF₄ shows quite clearly that boiling point is not simply related to any one of these: molecular mass, molar refraction (polarizability), total number of electrons, or number of valence shell electrons.

To paraphrase Dr. Johnson: we have found an argument, it is not easy to find an understanding.

Literature Cited

1. Rich, R. J. Chem. Educ. 1995, 72, 9–12.