Interfacial tension definition

Surface properties of proteins in general, 296-298 (table) purification methods based on, 272 Surface tension and interfacial properties, 609-628. see also Interfaces Surfactants, see also Interfacial tension definition and adsorption kinetics of, 617-618, 639... 

The molecules of liquids are separated by relatively small distances so the attractive forces between molecules tend to hold firm within a definite volume at fixed temperature. Molecular forces also result in tlie phenomenon of interfacial tension. The repulsive forces between molecules exert a sufficiently powerful influence that volume changes caused by pressure changes can be neglected i.e. liquids are incompressible. 

Double integration with respect to EA yields the surface excess rB+ however, the calculation requires that the value of this excess be known, along with the value of the first differential 3TB+/3EA for a definite potential. This value can be found, for example, by measuring the interfacial tension, especially at the potential of the electrocapillary maximum. The surface excess is often found for solutions of the alkali metals on the basis of the assumption that, at potentials sufficiently more negative than the zero-charge potential, the electrode double layer has a diffuse character without specific adsorption of any component of the electrolyte. The theory of diffuse electrical double layer is then used to determine TB+ and dTB+/3EA (see Section 4.3.1). 

Components of interfacial tension (energy) for the equilibrium of a liquid drop on a smooth surface in contact with air (or the vapor) phase. The liquid (in most instances) will not wet the surface but remains as a drop having a definite angle of contact between the liquid and solid phase. 

In a similar manner, an expression for the interfacial tension, Yf can be written using the geometric mean definition for work of adhesion, Wa (see Figure 8), and the Girifalco-Good interaction parameter (17-18), as. 

The amount of surface-active agent present may be so small that no measurable change in any physical property, including interfacial tension, can be detected. This is particularly true if the agent is a finely divided solid (El). Lindland and Terjesen (L4) showed that, after a definite but small concentration of surfactant had been used, further additions caused but little change in terminal velocity. 

It would be of considerable interest to have data for the surface and interfacial tensions of a pair of liquids such as nicotine and water which are miscible in all proportions except within a definite temperature range. Here we should expect to find curves of the type shown in the figure, where a and h represent the surface tensions of the two phases within the critical region and c their interfacial tension. The latter has no meaning either above or below the critical temperatures and must have a maximum at some intermediate point. 

The definition of interfacial tension given in Chapter 8 also applies to water-hydrocarbon systems. 

Equation D3.5.13 illustrated that the free energy of an interfacial system can be expressed in terms of the interfacial tension and chemical potential of the overall system. A simple differentiation or alternatively the reutilization of the definition of the interfacial tension used in Equation D3.5.7 at constant pressure and temperature yields ... 

With the help of this equation it is also possible to give a definition of the interfacial tension, which is equivalent to the previous definition ... 

Manual of Symbols and Terminology for Physicochemical Quantities and Units Appendix II. Definitions, Terminology and Symbols in Colloid and Surface Chemistry, part I. Pure and Appl. Chem. 31 (1972) 577. (This general recommendation also covers interfacial tensions and related topics.)... 

Having now encountered interfacial tension in the interfacial stress tensor it makes sense to review and compare the various definitions that we have so far encountered. 

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