Decane, surface tension

Estimate the surface tension of n-decane at 20°C using Eq. 11-39 and data in Table II-4. 

Dotnahska, U., Kozlowska, M.K., and Rogalski, M. Solubilities, partition coefficients, density, and surface tension for imidazoles -t octan-l-ol or -t water or -t n-decane, / Chem. Eng. Data, 47(3) 456-466, 2002. 

Cockbainf measured the interfacial tension of the water-decane surface at various concentrations of sodium dodecyl sulfate (NaDS). The experiments were done at 20°C both in the presence and absence of NaCl. Use the suitable form of the Gibbs equation in each case to calculate and a at 7 values of 10 and 20 dyne cm-1 from the following data ... 

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 solubility of the surfactant in decane is also quite small at 25°C, about 0.04 wt%, but over a narrow temperature range around 50°C it rises dramatically, as in the Krafft point range of a single-chain surfactant in water (11a). Such a phenomenon with a surfactant in a nonpolar solvent is not uncommon (35). Incidentally, the absence of a Krafft point range for the surfactant in water between 10 and 90°C argues for the absence of micelles in solution. Abrupt change in the slope of such a property as surface tension versus concentration (9) can be due to precipitation of a new phase as well as to onset of appreciable micelle formation, and so does not constitute conclusive evidence for the latter. 

Using the ADSA technique (cf. Rotenberg et al. 1983, Cheng et al. 1990), the adsorption of HA at the water/decane interface was studied (Miller et al. 1993a). At low concentrations an induction time is detectable (Fig. 5.40). At higher concentrations, of 0.015 and 0.02 mg/ml, the interfacial tensions tend to the same equilibrium value. A similar phenomenon was also observed at the water air interface. Even at extremely high HA concentrations of about 50 mg/ml the equilibrium surface tension values are not less than about 51 mN/m, a veilue which has already been reached at a concentration as low as 1 mg/ml. 

One peculiarity should be mentioned in the dependencies given in Fig. 5.38, which can be also seen in Fig. 5.40 for the two lower HA concentrations at the water/decane interface. Just after the formation of a fresh surface, the surface tension is higher than that of pure water/air or water/decane interface. This effect, which is much higher than the accuracy of the methods... 

Fig. 6.22 Interfacial tension relaxation of 0.02 mg/ml HA to three square pulses at 24°C at the water/decane interface a) drop area change, b) surface tension response according to Miller et al. (1993c)...

Properties of the three liquids of special interest are compared in Table I. The liquid surface tension, vlv > these reference liquids covers almost a threefold range at 20°C. In this same range are the surface tensions at 20°C. for the five other freshly purified liquids, formamide, hexachloropropylene, tert-butylnaphthalene, dicyclohexyl, and decane (58.2, 38.1,33.7, 32.8, and 23.9 dynes per cm., respectively). 

Figure 2.20 Dependence of surfactant content of surface tension of oligomeric systems at mercury interface (1) ED-20-OP-10 (2) ED-20-decane (3) ED-20-K)Ctane (4) ED-20-L-19 (5) PN 609-21M-OP-10 (6) PN 609-2IM-dibutyl phtha-late (DBP) (7) PN 609-21M-dimethyl phthalate (8) ED-20-ethanol (9) PN 609-21M-ATG.

Recently the DFT method combined with SAFT equations of state has been used to predict the interfacial properties of real fluids. LDA methods are accurate enough to treat liquid-liquid and liquid-liquid interfaces where the density profiles are usually smooth functions, and have been used in combination with the SAFT-VR approach to predict the surface-tension of real fluids successfully. The intermolecular model parameters required to treat real substances are determined by fitting to experimental vapour-pressure and saturated liquid density data in the usual way (see section 8.5.1) and the resulting model is found to provide accurate predictions of the surface tension. A local DFT treatment has also been combined with the simpler SAFT-HS approach, but in this case only qualitative agreement with experimental surface tension data is found due to the less accurate description of the bulk properties provided by the SAFT-HS equation. Kahl and Winkelman" have followed a perturbation approach similar to the one proposed with the SAFT-VR equation and have coupled a local DFT treatment with a Lennard-Jones based SAFT equation of state. They predict the surface tension of alkanes from methane to decane and of cyclic and aromatic compounds in excellent agreement with experimental data. 

Kellay et al. [42, 67] attribute the correlation between the maximum film thickness and the minimum oil-water interfacial tension in this decane-aqueous AOT system to the presence of thermally induced fluctuations at the oil-water surface. The maximum film thickness of 7 nm suggests that alkane molecules form a film that separates a probably weakly interdigitated monolayer from the air. Kellay et al. [42, 67] assume this film has a tension equal to that of the bulk oil-air surface. We then have a thin film with one surface having a high surface tension (the oil-air... 

Hough and White (1980) have shown that the critical length is inversely proportional to the square root of the fiquid density. This relationship can be used to predict the surface tensions with only one adjustable parameter, namely, the experimental critical length for some reference hydrocarbon. Use the//-value for n-decane as reference and estimate the predicted critical lengths and predicted surface tensions. Complete the last column of the table above and comment on the results. 

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