Octane/water systems

Interaction parameter was also generated for the hydrocarbon -rich phases of the n-octane - water system. The data of Kalafati and Piir (37j were used. There were no data available for the water - rich liquid phase for this binary. 

The view that the monomers are confined to the reverse micellar pseudophase is supported by interfacial tension data (67), which demonstrate that in a two-phase octane/water system, partially hydrolyzed TEOS species partition preferentially into the aqueous phase. The interfacial tension determined at the octane/water interface for samples prepared with precursor ethanolic solutions of different water-to-TEOS molar ratios (h - 0, 0.29, and 0.55) are presented in Figure 2.2.14 (67). As can be seen, for TEOS concentrations below about 4 X 10- 1 M, the octane/water interfacial tension is independent of the concentration of TEOS species in the organic phase... 

Shergold. H.L. and Mellgren, O., Concentration of minerals at the oil-water interface Hematite-iso-octane-water system in the presence of sodium dodecyl sulphate, Trans. IMMC, 78, 121, 1969. 

H. Watarai, M. Tanaka, and N. Suzuki, Determination of partition coefficients of halobenzenes in heptane/water and 1-octanal/water systems and comparison with the Scaled Particle calculation. Anal. Chem., 54(4), 702-705 (1982). 

In the absence of specific adsorption at the interface between immiscible electrolytes the potential drop occurs mainly in two diffuse layers contained in different phases. True enough, in the octane/water system there are practically no ions in the hydrocarbon phase in a concentration sufficient to screen the adsorption potential at the interface. Due to this fact, in investigating the processes in the electric double layer, it is possible to use the Volta potential measurements for determining the surface potential. The surface potential is known to consist of two terms ... 

The prosthetic groups of many membrane enzyme systems contain metalloporphyrins. Therefore, it is not surprising that an attempt has been made to reveal and study the catalytic effect of porphyrins during redox processes at the interface between immiscible liquids. Complexes of different metals with different porphyrins exhibited catalytic activity in the oil/water system [50]. First of all, let us consider the transformations of metal complexes of porphyrins in the octane/water system. In wet octane, as a result of the hydrolysis and dimerization reactions, FeEP changes to a //-complex and this results in a change in the absorption spectrum (Fig. 5). With a strong acidification of the aqueous phase, the equihbrium of Eqs. (12) and (13) shifts to the left and at pH 1 the positions of the maxima on the absorption spectra of ethioporphyrin in dry and wet octane coincide. 

Fig. 6. Dependence of NADH concentration on incubation time of an octane/water system at different initial NADH concentrations (indicated) in argon atmosphere -1-b. Medium 10" M FeEP 10" M vitamin K3 20 mM tris-HCl pH 7.5. Control without FeEP-2 [50]...

Aerobic oxidation of cytochrome c is accomplished by cytochrome c oxidase representing the terminal step of the respiratory chain of mitochondria. Cytochrome c oxidase can be considered as being the acceptor and donor of 4 electrons but for the present, the mechanism of molecular oxygen reduction remains a controversial issue [63]. The experiments with cytochrome c oxidase in the octane/water system... 

Fig. 15. Dependence of the displacement of the Volta potential in the octane/water system catalyzed by succinate-cytochrome c reductase on the concentration of succinate (a) and of cytochrome c (b). Incubation medium 0.05 M tris-HCl (pH 7.4) 0.5 mM cytochrome c, 0.1 mM MNQ, and 0.4 mg of sucdnate-cytochrome c reductase protein per ml (for b the incubation medium also contained 4 mM succinate)...

It was shown by special measurement that the reduction of MNQ by this enzyme complex in an aqueous medium is not suppressed by rotenone, while the electrogenic function of NADH-MNQ reductase in the octane/water system proved to be sensitive to rotenone. 

When an octane/water system containing chlorophyll a, DNP and K3Fe(CN)5 is illuminated with visible Ught, oxygen evolution takes place, accompanied by appearance of a positive photopotential [42, 43, 46, 48, 49, 65]. 

In Nature (on membranes of chloroplasts) water is oxidized by the four-electron mechanism and the life-time of chlorophyll can be as long as one day. In a model octane/water system, oxygen evolution occurs also during several hours. This is indirect evidence in favor of a many-electron reaction. Therefore we shall consider a four-electron mechanism of water oxidation sensitized by chlorophyll adsorbed at the oil/water interface proposed by Volkov [81]. It was shown above that the interface is the most likely site for the water photooxidation reaction. Thus it is assumed that water can be oxidized by a reaction complex adsorbed at the interface that consists of a hydrated oligometer of chlorophyll, a hydrophilic electron acceptor and hydrophobic proton acceptor [81,82,86]. The water in the reaction complex is linked coordinatively with the magnesium of one of the chlorophyll molecules, by hydrogen bonds with the carbonyl group of another chlorophyll molecule, and with the phenol anion also... 

The exit rate constants for cyclohexane and p-xylene from the micelles present in the cubic phase of the sodium octanoate/octane/water system have been measured by combining TRLQ and NMR self-diffusion data on the system. The value found for p-xylene compares well with that determined on the basis of solubility measurements. ... 

Table 7.6 Pre-exponent for the C12E5-octane-water system...

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