Interfacial parameters

The temperature dependence of the electrical double-layer parameters has been determined for real393,398 as well as quasi-perfect Ag planes.382,394 For quasi-perfect Ag electrodes, the value of 3 ffa0/9rhas been found to be higher for Ag(100) than for Ag(lll), and so it was concluded that Ag(lll) is more hydrophilic than Ag(100). For real surfaces,382,385,386 dEff=0/BT increases in the order (110) < (100) <(111). The same order of planes has been observed for Au 446-448 BEa /BT linearly increases as AX (interfacial parameter) decreases, i.e., as the hydrophilicity of Ag and Au electrodes decreases.15 32 393 397 398 446 48... 

Relative and Absolute Interfacial Parameter for Polycrystalline Metals in Contact with Water... 

Figure 21. Correlation between the enthalpy of formation of the oxide MO and the relative value of the interfacial parameter, AX, derived from Fig. 14.

Figure 25. Plot of the temperature coefficient of the potential of zero chaige for different crystal faces of Ag and Au, vs. the interfacial parameter, AX . From Ref. 32. (Reproduced from S. Trasatti and L.M. Donbova, J. Chem. Soc. Faraday Trans. 91,3318, Fig. 7, 1995 with permission of The Royal Society of Chemistry.)...

Figure 26. Plot of the Gibbs energy of adsorption of organic substances at a = 0 vs. the interfacial parameter, AX. (1) 1-Hexanol, (2) 1-pentanol, and (3) acetonitrile. From Ref. 32, updated. Additional points (1) Au(l 11),910 Bi(l 11),152 and (2) Ga916...

Figure 27. Gibbs energy of adsorption of water from the bulk of the solution on the given metals as calculated by Afanasyev and Akulova.909 The figures on top of the bars are the values of the interfacial parameter, AX.

Gibbs energy for the adsorption of water and the interfacial parameter, 187 Gokstein and the piezo electric method for the determination of the potential of zero charge, 42 Gold... 

Interfacial electron transfer, Marcus model inapplicability, 513 Interfacial parameter... 

Tafel plots, during electrode polymerization, 316 Technology of electrochemical polymer formation, 427 Temperature coefficient and the interfacial parameter, 183 and the potential of zero charge, 182 of potential of zero charge as a function of crystal phase, 87... 

All these processes occur either consecutively or simultaneously and are influenced by a range of interfacial parameters [38]. 

The basis for the foam properties is given by interfacial parameters. Although correlations have been shown between a single parameter and foam properties, there is still a lack in a general correlation between interfacial properties and the foam behavior of complex systems in detergency. The simplest approach to correlate interfacial parameters to foam properties is the comparison of the surface activity measured by the surface tension of a surfactant system and foam stability. 

Expression 6) - g (dip)o = X was given the name interfacial parameter by Trasatti. This parameter is not amenable to direct experimental detamination instead, a relative value of can be estimated from... 

The values for all metals studied are more negative than for Hg. A higher value of X indicates a stronger interaction of water with the metal surface. The interfacial parameter strongly depends not only on the kind of metal but also on the structure of the electrode surface. 

A similar correlation was found between the Gibbs energy of adsorption AG%ds and the interfacial parameter Mat = AG°adsincludes... 

The influence of the surface structure on the metal-water interaction has also been determined for silver electrodes (Table 3). There are discrepancies in the AG° values given by different authors for silver electrodes. For example, Vitanov and Popov obtained the same hydrophilicity sequence as for gold Ag(l 11) > Ag( 100). Another sequence based on the interfacial parameter was given by Trasatti. The interfacial... 

These ten interfacial parameters give a very complete description of the energetics of a detergency system. Further surface tension variables for a fluid-air or solid-air interface will also be used to evaluate these ten interfacial parameters. The remainder of this section will explore their evaluation. 

It is probable that numerous interfacial parameters are involved (surface tension, spontaneous curvature, Gibbs elasticity, surface forces) and differ from one system to the other, according the nature of the surfactants and of the dispersed phase. Only systematic measurements of > will allow going beyond empirics. Besides the numerous fundamental questions, it is also necessary to measure practical reason, which is predicting the emulsion lifetime. This remains a serious challenge for anyone working in the field of emulsions because of the polydisperse and complex evolution of the droplet size distribution. Finally, it is clear that the mean-field approaches adopted to measure > are acceptable as long as the droplet polydispersity remains quite low (P < 50%) and that more elaborate models are required for very polydisperse systems to account for the spatial fiuctuations in the droplet distribution. 

Using different polymeric materials in the chromatographic columns and LSC data on retention times (t) of suitably chosen reference solutes, three interfacial parameters (o(p, Ojj, and S), defined below, have been generated for characterizing polymeric membrane materials (53,56)... 

Fig. 6.116. Gibbs energy change for adsorption of amyl alcohol (1) and acetonitrile (2) on a number of sp-metals and Ag, as a function of the relative interfacial parameter. (Reprinted from S. Trasatti, Russ. J. Electrochem. 31 713, 1995, Fig. 8.)...

Key Concepts of Interfacial Properties in Food Chemistry CASE STUDY LIPID OXIDATION OF EMULSIONS The case of lipid oxidation in an emulsified system is a perfect example to illustrate the importance of interfacial properties in food chemistry. The goal of this case study is not to completely describe the very complex mechanisms of lipid oxidation in emulsions. Indeed, many investigators over the past years have focused on this research area. Instead, the key interfacial parameters that influence lipid oxidation in emulsions are emphasized. 

In several previous papers, the possible existence of thermal anomalies was suggested on the basis of such properties as the density of water, specific heat, viscosity, dielectric constant, transverse proton spin relaxation time, index of refraction, infrared absorption, and others. Furthermore, based on other published data, we have suggested the existence of kinks in the properties of many aqueous solutions of both electrolytes and nonelectrolytes. Thus, solubility anomalies have been demonstrated repeatedly as have anomalies in such diverse properties as partial molal volumes of the alkali halides, in specific optical rotation for a number of reducing sugars, and in some kinetic data. Anomalies have also been demonstrated in a surface and interfacial properties of aqueous systems ranging from the surface tension of pure water to interfacial tensions (such as between n-hexane or n-decane and water) and in the surface tension and surface potentials of aqueous solutions. Further, anomalies have been observed in solid-water interface properties, such as the zeta potential and other interfacial parameters. 

The basis for the foam properties is given by interfacial parameters. An overview of some interfacial parameters and the correlation to foam properties is shown in Figure 3.30 [9]. 

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