1. “For each hotness there is some body whose latent heat at that hotness fails to vanish for some volume.” This is called the “Thermometric axiom”; and, since it has to do with latent heat, it seems appropriate that it should have been formulated by J. B. Boyling [Proc. R. Soc. London
329, 35 (1972)].
2. The idea that a one-component system has in principle properties which are continuous through the phase change, embodied in Figure 4.1.1, is originally due to Van der Waals, Die Continuitat des Gasformingen und Flussigen Zustandes, J. A. Barth, Leipzig (1881).
3. The question of pressure and temperature being continuous across an interface between two phases presents some subtlety. For instance, shock waves in gases are phenomena where both temperature and pressure are discontinuous; however, the discontinuity travels through the gas and is sustained by a nonequilibrium phenomenon. The point is discussed in detail in any book on gas dynamics. Discontinuities of temperature, chemical potential, and velocity can also occur in nonequilibrium phenomena; the whole question is discussed in a recent review paper by G. Astarita and R. Ocone, Adv. Chem. Eng. (to be published).
4. Phase equilibria are discussed in all thermodynamics textbooks. For the case of mixtures, a very complete discussion is given by M. B. King, Phase Equilibria in Mixtures, Pergamon Press, Oxford (1969).
5. Phase equilibria in continuous mixtures have been discussed in a number of papers; the recent one by S. K. Shibata, S. I. Sandler, and R. A. Behrens, Chem. Eng. Sci.
42, 1977 (1987) is a good guide to the relevant literature.