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The role of interfacial tension

In all the preceding discussion of terms having the gAy form, yhas been interpreted as a surface tension, the factor g serving to correct for the molecular-scale curvature effect. But a stuface tension is measured at the macroscopic air-liquid interface, and in the solution case we are actually interested in the tension at a molecular scale solute-solvent interface. This may be more closely related to an interfacial tension than to a surface tension. As a consequence, if we attempt to find (say) g2A2 by dividing by we may be dividing by the wrong munber. [Pg.302]

To estimate ntunbers approximating to interfacial tensions between a dissolved solute molecule and a solvent is conjectural, but some general observations may be helpful. Let yx and Yi. be stuface tensions (vs. air) of pine solvents X and Y, and yxv the interfacial tension at the X-Y interface. Then in general. [Pg.302]

On the basis of the preceding arguments it is recommended that gAy terms (exemplified by g A y, 2 2 29 nd gA(y2-y)) should not be factored into gA quantities through division by y, the smface tension, (except perhaps to confirm that magnitudes are roughly as expected). This conclusion arises directly from the interfacial tension considerations. [Pg.302]

when K, = 1 and Kj = 1, eq. [5.5.13] shows that AG, ,v = AGwwl 1 this special case the solvation energy is eomposition-independent. [Pg.304]

Leffler and E. Grunwald, Rates and Equilibria of Organic Reactions, J. Wiley Sons, New York, [Pg.304]

LePree, M.J. MulsM, andK.A. Connors, J Chem. Soc., Perkin Trans. 2, 1491 (1994). [Pg.304]


This transition may j-.e. reducing the specific surface energy, f. The reduction of f to sufficiently small values was accounted for by Ruckenstein (15) in terms of the so called dilution effect". Accumulation of surfactant and cosurfactant at the interface not only causes significant reduction in the interfacial tension, but also results in reduction of the chemical potential of surfactant and cosurfactant in bulk solution. The latter reduction may exceed the positive free energy caused by the total interfacial tension and hence the overall Ag of the system may become negative. Further analysis by Ruckenstein and Krishnan (16) have showed that micelle formation encountered with water soluble surfactants reduces the dilution effect as a result of the association of the the surfactants molecules. However, if a cosurfactant is added, it can reduce the interfacial tension by further adsorption and introduces a dilution effect. The treatment of Ruckenstein and Krishnan (16) also highlighted the role of interfacial tension in the formation of microemulsions. When the contribution of surfactant and cosurfactant adsorption is taken into account, the entropy of the drops becomes negligible and the interfacial tension does not need to attain ultralow values before stable microemulsions form. [Pg.159]

A.I. Rusanov, Fazovye Ravnoveciya i Poverkhnostnye Yavleniya (Khlmiya, USSR, 1967). German transL, Phasengleichgewichte und Grenzflachenerscheinungen. Akademie Verlag DDR, 1978.) (Thorough thermodynamic analysis on the role of interfacial tensions in phase equilibria.)... [Pg.202]

Problem 2-21. Fluid Statics. When a cylindrical tank of liquid is rotated at constant angular velocity free surface attains a steady shape. If the undisturbed (nonrotating) height of the liquid is h, determine the shape of the interface. Be sure to state any and all assumptions. What is the role of interfacial tension When can it be neglected ... [Pg.104]

Strassner (127) examined a third eomponent, waxes . He showed that resin and waxes do not oil-wet siliea. Waxes had no significant effect. He eoncluded that the waxes only contribute to increased viscosity of the oil phase. At low salt concentrations asphaltenes plus resins will oil-wet silica at acidic pH, but will water-wet siliea at basie pH. He examined Venezuelan crude oil and distilled water, and found the most breakout of water occurred at pH 10. In this case there was a transition to a mobile weak film, and interfacial tension was still high. However, when the water was changed to a bicarbonate solution, this transition occurred at pH 6, where maximum water breakout was observed at the high interfacial tension. The role of interfacial tension is discussed later in this text. [Pg.555]

For illustrative purposes, we will now consider the role of interfacial tension on the stability of emulsions. A majority of researchers [Bickerman (11)] agreed that since emulsions possess very high interfacial area when the interfacial tension is reduced one expects an increased emulsion stability. Adamson (12) stated, "interfacial tension criterion is unassailable. It is also relatively useless except for qualitative arguments."... [Pg.348]

G. Reiter, R. Khanna, and A. Sharma, Self-destruction and dewetting of thin polymer films the role of interfacial tensions, J. Phys. Condens. [Pg.187]

In this chapter, we turn our attention to binary mixtures of different polymers. These are perhaps better termed pseudo-binary because here we do not consider molecular weight distribution effects of polymer chains of different molecular weights as independent species. Our hrst concern is with miscibility, as it was with polymer-solvent systems in Chapter 3 and with polymer-additive systems in Chapter 4. We consider which polymer structures are likely to lead to miscibility. This leads to a consideration of partially miscible systems and to mixtures involving copolymers. Finally, we consider immiscible polymer blends. Here we emphasize the role of interfacial tension between phases and the factors influencing phase morphology. [Pg.157]

Chan, M. Yen, T.F. Role of Sodium Chloride in the Lowering of Interfacial Tension Between Crude Oil and Alkaline Aqueous Solution, Fuel, 1981, 60, 552. [Pg.407]

Figure 1.28. Role of interfacial tension on fragmentation. ( ) Surfactant concentration 5 wt% —5 mN/m (A) PVAAc 15 wt%—17 mN/m. The lines are visual guides. (Adapted from [137].)... Figure 1.28. Role of interfacial tension on fragmentation. ( ) Surfactant concentration 5 wt% —5 mN/m (A) PVAAc 15 wt%—17 mN/m. The lines are visual guides. (Adapted from [137].)...
Apart from their effect on reducing y, surfactants play major roles in the deformation and break-up of droplets, and this is summarised as follows. Surfactants allow the existence of interfacial tension gradients which is cracial for the formation of stable droplets [8]. In the absence of surfactants (clean interface), the interface cannot withstand a tangential stress, and the liquid motion will be continuous (Figure 10.17a). [Pg.179]

In many lipid-based food systems, in addition to performing rheological experiments to determine global structure, the measurement of surface rheological properties can play a crucial role in determining the quality of the final product. Therefore, the measurement of interfacial tension is sometimes a matter of utmost importance. It is particularly valuable for dispersed lipid food systems, primarily for W/O or... [Pg.82]

It is well established that ultralow interfacial tension plays an important role in oil displacement processes [16,18]. The magnitude of interfacial tension can be affected by the surface concentration of surfactant, surface charge density, and solubilization of oil or brine. Experimentally, Shah et al. [23] demonstrated a direct correlation between interfacial tension and interfacial charge in various oil-water systems. Interfacial charge density is an important factor in lowering the interfacial tension. Figure 6 shows the interfacial tension and partition coefficient of surfactant as functions of salinity. The minimum interfacial tension occurs at the same salinity where the partition coefficient is near unity. The same correlation between interfacial tension and partition coefficient was observed by Baviere [24] for the paraffin oil-sodium alkylbenzene sulfonate-isopropyl alcohol-brine system. [Pg.747]

The word acid is a good example. A discussion of its meaning is relevant in this book because Acid-base interactions play a significant role in considerations of the theory of interfacial tension and of adhesion. [Pg.12]

Lin JN, Banerji SK, Yasuda H. Role of interfacial tension in the formation and the detachment of air bubbles a single hole on a horizontal plane immersed in water. Langmuir 10 936-942, 1994. [Pg.808]

The role of interfacial deformation is considered in the stability analysis of fluid layers heated from below or above when there is an open interface to ambient air, and double diffusive transport of heat and solute thus leading to variations of interfacial tension that compete or cooperate with buoyancy phenomena. The onset of both oscillatory convection and steady patterns is described. [Pg.223]

The study of interfacial tension between two immiscible low molecular weight liquids dates to the 19 century [43, 52, 53] and was discussed by Maxwell [43] among others in this period. It has been recognized by many researches that interfacial tension plays a key role in determining the shape, breakup, and coalescence of dispersed phases. [Pg.167]

It is quite clear, first of all, that since emulsions present a large interfacial area, any reduction in interfacial tension must reduce the driving force toward coalescence and should promote stability. We have here, then, a simple thermodynamic basis for the role of emulsifying agents. Harkins [17] mentions, as an example, the case of the system paraffin oil-water. With pure liquids, the inter-facial tension was 41 dyn/cm, and this was reduced to 31 dyn/cm on making the aqueous phase 0.00 IM in oleic acid, under which conditions a reasonably stable emulsion could be formed. On neutralization by 0.001 M sodium hydroxide, the interfacial tension fell to 7.2 dyn/cm, and if also made O.OOIM in sodium chloride, it became less than 0.01 dyn/cm. With olive oil in place of the paraffin oil, the final interfacial tension was 0.002 dyn/cm. These last systems emulsified spontaneously—that is, on combining the oil and water phases, no agitation was needed for emulsification to occur. [Pg.504]

If an ionic surfactant is present, the potentials should vary as shown in Fig. XIV-5c, or similarly to the case with nonsurfactant electrolytes. In addition, however, surfactant adsorption decreases the interfacial tension and thus contributes to the stability of the emulsion. As discussed in connection with charged monolayers (see Section XV-6), the mutual repulsion of the charged polar groups tends to make such films expanded and hence of relatively low rr value. Added electrolyte reduces such repulsion by increasing the counterion concentration the film becomes more condensed and its film pressure increases. It thus is possible to explain qualitatively the role of added electrolyte in reducing the interfacial tension and thereby stabilizing emulsions. [Pg.508]

The role of the cosurfactant in reducing the interfacial tension can be understood from application of the Gibbs adsorption equation in the form (14). [Pg.171]

The low interfacial tensions between two liquids have been measured for different systems by using the pendant drop method. In the case of the quaternary system Ci2ll25S 3 tNa+H20+n-Butanol+Toluene, the interfacial data as measured by pendant drop method are compared with reported literature data, using other methods (with varying NaCl concentration). In order to understand the role of co-surfactant, ternary systems were also investigated. The pendant drop method was also used for measuring the interfacial tension between surfactant-H20/n-alcohol (with number of carbon atoms in alcohol varying from 4-10). The interfacial tension variation was dependent on both the surfactant and alcohol. [Pg.329]


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Interfacial tension

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