Liquid interfacial tension

A zero or near-zero contact angle is necessary otherwise results will be low. This was found to be the case with surfactant solutions where adsorption on the ring changed its wetting characteristics, and where liquid-liquid interfacial tensions were measured. In such cases a Teflon or polyethylene ring may be used [47]. When used to study monolayers, it may be necessary to know the increase in area at detachment, and some calculations of this are available [48]. Finally, an alternative method obtains y from the slope of the plot of W versus z, the elevation of the ring above the liquid surface [49]. 

The entropically driven disorder-order transition in hard-sphere fluids was originally discovered in computer simulations [58, 59]. The development of colloidal suspensions behaving as hard spheres (i.e., having negligible Hamaker constants, see Section VI-3) provided the means to experimentally verify the transition. Experimental data on the nucleation of hard-sphere colloidal crystals [60] allows one to extract the hard-sphere solid-liquid interfacial tension, 7 = 0.55 0.02k T/o, where a is the hard-sphere diameter [61]. This value agrees well with that found from density functional theory, 7 = 0.6 0.02k r/a 2 [21] (Section IX-2A). 

Gravitational force favors the separation of gas from liquid in a disperse system, causing the bubbles to rise to the hquid surface and the liquid contained in the bubble walls to drain downward to the main body of the liquid. Interfacial tension favors the coalescence and ultimate disappearance of bubbles indeed, it is the cause of bubble destruction upon the rupture of the laminae. 

Decreased liquid-liquid interfacial tension (when compared with a gas-liquid system) results in higher liquid-liquid interfacial areas, which favor solid-particle droplet collisions. 

The Good-Girifalco theory [77-82] was originally formulated to make an attempt to correlate the solid-liquid interfacial tension to the solid surface energy and the liquid surface tension through an interaction parameter, basic formulation of the theory is ... 

Induction period measurements can also be used to determine interfacial tensions. To validate the values inferred, however, it is necessary to compare the results with an independent source. Hurley etal. (1995) achieved this for Cyanazine using a dynamic contact angle analyser (Calm DCA312). Solid-liquid interfacial tensions estimated from contact angle measurements were in the range 5-12 mJ/m which showed closest agreement with values (4—20mJ/m ) obtained from the log-log plots of induction time versus supersaturation based on the assumption of — tg. 

In the absence of specific interactions of the receptor - ligand type the change in the Helmholtz free energy (AFadj due to the process of adsorption is AFads = yps - ypi - Ysi, where Yps, YPi and ys, are the protein-solid, protein-liquid and solid-liquid interfacial tensions, respectively [5], It is apparent from this equation that the free energy of adsorption of a protein onto a surface should depend not only of the surface tension of the adhering protein molecules and the substrate material but also on the surface tension of the suspending liquid. Two different situations are possible. 

The rheological properties of a fluid interface may be characterized by four parameters surface shear viscosity and elasticity, and surface dilational viscosity and elasticity. When polymer monolayers are present at such interfaces, viscoelastic behavior has been observed (1,2), but theoretical progress has been slow. The adsorption of amphiphilic polymers at the interface in liquid emulsions stabilizes the particles mainly through osmotic pressure developed upon close approach. This has become known as steric stabilization (3,4.5). In this paper, the dynamic behavior of amphiphilic, hydrophobically modified hydroxyethyl celluloses (HM-HEC), was studied. In previous studies HM-HEC s were found to greatly reduce liquid/liquid interfacial tensions even at very low polymer concentrations, and were extremely effective emulsifiers for organic liquids in water (6). 

Liquid liquid interfacial tension, and density difference, in the immiscible (monotectic) alloy (Al34 5Bi<55 5)95Si5 (mass%) have been measured by Kaban and Hoyer (2006). Addition of Si to the binary Al-Bi alloy increases the interfacial tension between the Al-and Bi-rich liquid phases. 

From the above equations it is also apparent that in horizontal two-phase flow, all irreversibilities appear as wall friction, provided gas-liquid interfacial tension effects are neglected. 

A drop of liquid at rest on a solid surface is under the influence of three forces or tensions. As shown in Fig. 10.2, the circumference of the area of contact of a circular drop is drawn toward the center of the drop by the solid-liquid interfacial tension, 7sl- The equilibrium vapor pressure of the liquid produces an adsorbed layer on the solid surface that causes the circumference to move away from the drop center and is equivalent to a solid-vapor interfacial tension, ygy- The interfacial tension between the liquid and vapor, y y, essentially equivalent to the surface tension y of the... 

However, the surface tension of the solid, ySG, and the solid—liquid interfacial tension, ySL, cannot be measured direcdy by simple means. The work of adhesion of the solid to the liquid SL, is usually determined by other techniques. 

Miller, C. A., and Neogi, P., Interfacial Phenomena Equilibrium and Dynamic Effects, Marcel Dekker, New York, 1985. (Graduate level. An advanced-level textbook with a focus on interfaces between liquids, interfacial tension, and dynamics of interfaces.)... 

Here, R is the radius of the droplets and 7 is the liquid-liquid interfacial tension (see Section 13.5 and Table 13.2). The amount of AGem is equal to the Gibbs free energy gained upon demulsification. 

One concerned with the measurement of gas-liquid interfacial tension should consult the useful reviews of methods prepared by Harkins [in Chap. 9 of Weissberger, Techniques of Organic Chemstry, 2d ed., vol. 1, part 2, Interscience, New York, 1949), Schwartz and coauthors [Surface Acttve Agents, vol. 1, Interscience, New York, 1949, pp. 263-271 Surface Active Agents and Detergents, vol. 2, Interscience, New York, 1958, pp. 389-391, 417-418], and by Adamson [Physical Chemistry of Surfaces, Interscience, New York, I960]. 

Specifically, pore condensation represents a confinement-induced shifted gas-liquid-phase transition [20], This means that condensation takes place at a pressure, P, less than the saturation pressure, of the fluid [2,4,5], The x = P/P0 value, where pore condensation takes place, depends on the liquid-interfacial tension, the strength of the attractive interactions between the fluid and pore walls, the pore geometry, and the pore size [20],... 

Contact angles provide a unique means of determining solid-vapor and solid-liquid interfacial tensions because of the Young equation... 

Because solid-liquid interfacial tensions are always positive or zero, as a limiting case, it follows that AFtoh < 0, implying that, in the absence of electrostatic... 

Increase in the bubble velocity Vs favors bed contraction. At Vsup = 0 = gq, Vs represents the rise velocity of bubble in a stagnant liquid. Since the rise velocity of a single bubble increases with gas-liquid interfacial tension, it follows that any decrease in surface tension favors expansion. This effect of surface tension has been observed by, among others, Dakshinamurty et al. (1971) and Kim et al. (1975). 

A number of experimental techniques are available to obtain information on some aspects of the structure of liquids near surfaces. It should be realized at the onset that measuring the solid-liquid interfacial tension y " does not belong to this category because it is a thermodynamically inoperable quantity. One cannot Isothermally and reversibly extend interfaces with solids (see sec. 1.2.24). From contact angles one can obtain y but there are no thermodynamically operational procedures to split this difference into its constituents, although models which do this are available (Volume III). 

Diffusivity or viscosity Solid-liquid interfacial tension Water/solvent activity Boiling/melting point Solute activity (concentration)... 

While the classical theory of nucleation is limited by the implicit assumptions in its derivation, it successfully predicts the nucleation behavior of a system. Inspection of the equation above clearly suggests that the nucleation rate can be experimentally controlled by the following parameters molecular or ionic transport, viscosity, supersaturation, solubility, solid-liquid interfacial tension, and temperature. 

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