Phase equilbrium

Fig. 5. Relationship between the log Koc for phenanthrene sorption and the aliphaticity of humic acids, sequentially extracted from a soil. F-l, F-4, F-7, and F-9 are the first, fourth, seventh, and nineth extracted humic acids, respectively. 0.005, 0.05, and 0.5 pg mL are selected liquid-phase equilbrium concentrations of phenanthrene (Kang and Xing 2005).

Htitz, U., Englezos, P., Measurement of Structure H Hydrate Phase Equilbrium and Effect of Electrolytes, in Proc. 7th International Conference on Fluid Properties and Phase Equilibria for Chemical Process Design (1995). 

If the clusters do spend times long enough to exhibit equilibrium properties characterisic of a phase, then we can justifiably identify that phase as a stable species in the ensemble. If two such phase-like forms appear by satisfying the condition of observability in equilibrium, then we may identify the condition of the ensemble as one of phase equilbrium. However this is as much an equilibrium of chemical isomers as it is of phases, in the sense that each of the persistent forms can be assigned a well-defined free energy. Given that, we can immediately construct a traditional equilibrium constant K q for the ratio of concentrations or partial pressures of the two species,... 

A problem with concentration (or partial pressure) as used in Pick s law is that the respective component concentrations (or partial pressures) are different within two phases at equilibrium, save in the case of homogeneous azeotropes. Therefore, this phase-equilbrium feature of absolute activity is not apparent. It can be accommodated, however, by assigning an equilibrium absolute activity to the one phase that, by definition, would be equal to that of the other. This accommodation is most apparent in its assignment to the behavior of vapor-liquid systems. 

The first point in developing the thermodynamic method is the observation that for equilbrium between two phases-say, a and 3-the chemical potential must be equal in both phases for all components ... 

The number of components is the minimum number of independent species required to define the composition of all of the phases in the system. The simplest example usually cited to demonstrate the concept of components is that of water, which can exist in various equilibria involving the solid, liquid, and gas. In such a system there is one component. Likewise for acetic acid, even though it associates into dimers in the solid, liquid, and gaseous state, the composition of each phase can be expressed in terms of the acetic acid molecule and this is the only component. The important point for such a system is that the monomer-dimer equilibrium is established very rapidly, that is, faster than the time required to determine, say, the vapour pressure. In the cases in which the equilbrium between molecular species is established more slowly than the time required for a physical measurement, the vapour pressure, for example, will no longer be a function only of temperature, but also of the composition of the mixture, and the definition of a component acquires a kinetic aspect. 

Adsorption. In the design of the adsorption step of gas-phase processes, two phenomena must be considered, equiLbrium and mass transfer. Sometimes adsorption equiLbrium can be regarded as that of a single component, but more often several components and then interactions must be accounted for. Design techniques for each phenomenon exist as weU as some combined models for dynamic performance. 

Equilibrium. Among the aspects of adsorption, equiLbrium is the most studied and pubLshed. Many different adsorption equiLbrium equations are used for the gas phase the more important have been presented (see section on Isotherm Models). Equally important is the adsorbed phase mixing rule that is used with these other models to predict multicomponent behavior. 

Salager, J.L., Loaiza-Maldonado, I., Minana-Perez, M., and Silva, E, Surfactant-oil-water systems near the affinity inversion. Part I Relationship between equilbrium phase behavior and emulsion type and stability, J. Disp. Sci. Technol, 3, 279, 1982. 

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