RESUMEN
Henry's law is found by applying the condition of extremum to the Gibbs function of a fluid film. The resulting equation relates linearly the thickness of the adsorbed layer to the external gas pressure. The equation reveals that the coefficient of proportionality beta depends inversely on the saturation pressure p0. It also shows that wetting effects are irrelevant. These results predicted by the present model are in agreement with experiment. Copyright 1998 Academic Press.
RESUMEN
A thermodynamic description of condensation of droplets on ions is presented. The Gibbs free energy of noninteracting droplets in equilibrium with their vapor is a function of the number of moles, temperature, pressure, and surface tension G (p(r), T, sigma, n1g, ellipsis, ncg; n1l, ellipsis, ncl; ncl; n1sigma, ellipsis, ncsigma). From the variation around equilibrium of G, an equation relating saturation pressure and droplet size is obtained. The saturation ratio is considerably reduced by adding an ionic salt (the solute). Ion hydration allows the formation of stable droplets in an unsaturated environment. Their effect prevails at small values of the droplet radius r where the equation exhibits a stable branch and predicts condensation, even in the case of a perfect ionic solution. The equation also shows that an ionic mixture behaves as a pure solvent (metastable branch, Kelvin limit) for large r. We compare our results with those previously obtained. Copyright 1997Academic Press
RESUMEN
The temperature dependence of the thickness of a nonfreezing water interlayer confined between an ice core and a smooth surface of quartz capillary is studied here theoretically. By using the principle of conservation of energy a first order differential equation is found. The equation relates the temperature and the film thickness via the film pressure (disjoining pressure). Molecular and structural components of this pressure are examined. Nonequilibrium and equilibrium solutions are compared with the respective experimental data. It is shown that disjoining pressure forces cause the lowering of the temperature in systems having confined phases.