Dissociation Treatment of Condensing Systems III. Properties of Saturated Vapors of H2O, NH3, CH3Cl and CO2

It is found that the dissociation treatment previously described gives a satisfactory theory of the saturated vapor pressure curves in temperature ranges not too close to the critical point. Curves are given for PV/NkT and for surface energy in the cases of H2O, NH3, CH3Cl and CO2. In the case of H2O there remains an appreciable discrepancy in the energy curves at low values of T/Tc. It is suggested that this may be removed by taking into account the small size of the clusters involved in the equilibrium between vapor and liquid: the surface energy in a cluster may differ from that for the liquid in bulk. A method of estimating mean cluster sizes is suggested, which leads to reasonable results.