Phase contact systems

Contact-Angle Hysteresis A phenomenon manifested by differing values of advancing and receding contact angles in the same three-phase contact system. Both may differ from the equilibrium contact angle. See also Contact Angle. 

For the solid-liquid system changes of the state of interface on formation of surfactant adsorption layers are of special importance with respect to application aspects. When a liquid is in contact with a solid and surfactant is added, the solid-liquid interface tension will be reduced by the formation of a new solid-liquid interface created by adsorption of surfactant. This influences the wetting as demonstrated by the change of the contact angle between the liquid and the solid surface. The equilibrium at the three-phase contact solid-liquid-air or oil is described by the Young equation ... 

In addition to these relatively simple liquid phase aqueous systems, it is necessary to identify situations in which any of these aqueous phase reservoirs come into physical and chemical contact with solid surfaces (e.g., rocks, biomass, sediments, soils, magma etc.). In general, the presence of two or more phases (liquid plus one or more solid phase) provides important constraints on the chemical reactions that may occur within the system as a whole. 

The Volta potential, A very often called the contact potential, is the difference between the outer potentials of the phases, which are in electrochemical equilibrium in regard to the charged species, i.e., ions or electrons. Each two-phase electrochemical system, including a w/s system, may be characterized by the commonly known relation ... 

Depending on the nature of the system, the adsorption process can be either reversible or irreversible. In the first case an adsorption equilibrium exists between the particles adsorbed on the adsorbent s surface and the particles in the electrolyte (or in any other phase contacting with the adsorbent). After removing the substance from the electrolyte, adsorbed particles leave the surface and reenter into the electrolyte. In the case of an irreversible adsorption, the adsorbed particles remain at the surface even if their concentration in the bulk phase drops to zero. In this case the adsorbed particles can be removed from the surface only by means of a chemical reaction... 

In an earlier study calorimetry achieved this objective for the compositional boundaries between two and three phases (2). Such boundaries are encountered both in "middle-phase microemulsion systems" of low tension flooding, and as the "gas, oil, and water" of multi-contact miscible EOR systems (LZ). The three-phase problem presents by far the most severe experimental and interpretational difficulties. Hence, the earlier results have encouraged us to continue the development of calorimetry for the measurement of phase compositions and excess enthalpies of conjugate phases in amphiphilic EOR systems. 

Three-phase reactor systems are ideally suited for methanol production because of the ability to provide intimate contact between the gaseous phase reactants and the solid phase catalysts and to remove the large amounts of heat created by the high heats of reaction. In the three-phase system, an inert liquid phase circulates between the reactor and an external... 

Carroll, B.J, (1976). The accurate measurement of contact angle, phase contact areas, drop volume, and Laplace excess pressure in drop-on-fiber system. J. Colloid. Interface Sci. 57, 488-495. 

In a sense, all the present papers treat problems in interphase contacting. On the theoretical and observational sides, respectively, Davies and Kintner explore the properties of two-phase systems undergoing mass transfer. In a third study, both the descriptive and the theoretical properties of cocurrent two-phase flow systems are presented by Scott. Longitudinal dispersion (or axial mixing), which has only recently been identified and analyzed as a substantial factor in equipment performance, is reviewed by Levenspiel and Bischoff. 

Here, also we have extended (10) our treatment of synergism to 2-phase liquid systems and have derived equations that are completely analogous to those obtained for solutions in contact with air, when the nonaqueous phase is a hydrocarbon. The interaction parameter,... 

Materials in the whole system must be appropriate, that means reactor and piping for ozone gas as well as for ozonated water must be chosen carefully. For example, the material of the reactor and sampling system, especially the seals, has also to be chosen to avoid not only corrosion from ozone, but adsorption of the compound(s) being studied. It is advisable to let the liquid phase contact only glass and stainless steel. In stirred reactors for example, the stirrer seals (unless the stirrer is a magnetic bar) and all connectors for piping are best placed at the top of the reactor, so that the liquid does not come in contact with them. 

The vapor-phase contact oxidation of toluene was conducted in a conventional flow system. The reactor was made of a steel tube, 50 cm long and 1.8 cm I.D., mounted vertically and immersed in a lead bath. Air or a mixture of oxygen and nitrogen was introduced from the top of the reactor, with toluene being injected into the preheating section of the reactor by means of a syringe pump. 

Complexation of inorganic cations such as alkaline or alkaline earth metals by macrocyclic polyethers produces large, lipophilic cationic metal-macrocycle complexes that are readily soluble in nonpolar solvents such as benzene, toluene and haloalkanes. In order to maintain charge balance, the cationic complex has an associated counter anion. In an immiscible two-phase liquid system, such as a mixture of chloroform and water, the anion is necessarily pulled into the organic phase as the cationic complex crosses the phase boundary. A simple illustration of this principle is obtained by addition of a chloroform solution of [18]crown-6 to an aqueous solution of potassium picrate (potassium 2,4,6-trinitrophenolate). The yellow colour of the picrate anion is transported rapidly into the contiguous (physically in contact) chloroform phase upon agitation (Figure 3.43). 

Because of interference from the radioactive decay of other nuclides (which are typically formed with much higher yields), extraction systems with relatively high decontamination factors from actinides, Bi, and Po must be chosen, and the transactinide activity can only be measured in the selectively extracting organic phase. For this reason, measurement of distribution coefficients is somewhat difficult. By comparing the Rf or Db detection rate under a certain set of chemical conditions to the rate observed under chemical control conditions known to give near 100% yield, distribution coefficients between about 0.2 and 5 can be determined. If the control experiments are performed nearly concurrently, many systematic errors, such as gas-jet efficiency and experimenter technique, are cancelled out. Additionally, extraction systems which come to equilibrium in the 5-10 second phase contact time must be chosen. 

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