Sodium bromide (NaBr) or sodium salicylate (NaSal) can be added to aqueous solutions of cetyltrimethylammonium bromide (CTAB) to convert spherical micelles to rod-like (cylindrical) micelles that are believed to be necessary for the surfactant to be an effective drag-reducing agent. The effects of the added salt (inorganic or aromatic) on the micellization behavior have been tested by several available molecular-thermodynamic models. Models proposed both by Blankschtein and coworkers and by Nagarajan and coworkers show ability to predict the effects of nonadsorbing salts such as NaBr on the micellization of CTAB solutions. However, their application is limited when the additive is an organic salt (e.g., NaSal) providing that ions penetrate into the surfactant (e.g., CTAB) micelles. A model that combines the molecular thermodynamic approach with energetic and structural data obtained from atomistic scale Monte Carlo simulations of the micelle shell, has been developed (27) that predicts the micellization behavior of pure CTAB aqueous solutions and also performs well for the system with penetrating organic ions. The Monte Carlo simulation data from the complementary model show that intramicellar molecular ordering is crucial to the estimation of free energies and that ordering is affected by the curvature of the micelles. Finally, it was shown that the molecular ordering of the salicylate ions causes the deviation from the ideal mixing of the CTA(+) and Sal(-) ions, especially for cylindrical micelles. (C) 2003 American Chemical Society.

An analytically solvable lattice model was used to study the difference ill the physics of p-xylene adsorption in ORTHO and PARA phases of silicalite. The model predicts that a phase transition of p-xylene in the pore space does riot necessarily require a silicalite-phase transition. Conditions for the sorbate-phase transition are identified. The sign of the sorbate-sorbate interactions is critical to sorbate-phase transition. It is suggested that although the sorbate- and sorbent-phase transitions call he distinct events, there is strong coupling between the two. It is reasonable to suppose that the fluid-phase change may drive the zeolite phase change. Finally, this equilibrium study suggests the possibility of hysteresis at higher coverages depending on the kinetics of adsorption.

A pairwise interatomic potential has been used to investigate elastic and structural properties of two cubic zeolites: sodalite and dehydrated zeolite A. Constant volume energy minimization has been used to determine the variation of lattice constants and atomic coordinates with pressure. The calculated structures of sodalite and dehydrated zeolite A obtained at zero pressure are in reasonably good agreement with the available experimental values. We find that the structures at zero pressure are largely determined by the Coulomb potential. The pressure dependence of bond lengths and bond angles show that both sodalite and dehydrated zeolite A are easily deformed by bending the Si–O–Al angles. As expected for a less dense crystal, the dehydrated zeolite A is softer than the sodalite. We have also obtained the equation of state of these materials.

Macro- and microstructures of highly concentrated water-in-oil (W/O) emulsions were investigated in a water (or brine)/tetraethylene glycol dodecyl ether/decane system by means of phase studies, VEM (video-enhanced microscopy), and NMR self-diffusion coefficient measurements. The W/O emulsion consists of a small portion of oil or surfactant phase (continuous medium) and a large amount of water phase containing monomeric surfactant. The effects of temperature and NaCl on the stability were observed by VEM. In the water-rich corner of the main miscibility gap of the ternary phase diagram, the two-phase system can be classified into regons of stable emulsions and regions of extremely unstable emulsions. The NMR self-diffusion coefficient measurements show that the continuous phase is a reverse micellar solution in the stable-emulsion region but it is a bicontinuous microemulsion in the extremely unstable-emulsion region.

Prints containing the maximum amount of micrograph detail are the objective of all microscopists. Due to the limited dynamic range of printing papers (Fig. 1), much darkroom time is spent in printing wide tonal-range micrographs that require contrast manipulation. We have applied the technique of unsharp masking to simplify contrast reduction and developed a process that yields significantly better results in a shorter time than the conventional method of dodging and burning. Spiegler and Juris's early works in unsharp masking have been applied by various researchers to aerial mapping, graphic arts, astronomy, and, to a limited extent, to electron micrographs. We have built upon this work and developed a simple procedure for using unsharp masking and studied the quantitative effects of its use in dynamic range control and image enhancement.

ChemInformVolume 18, Issue 7 Article ChemInform Abstract: Patterns of Phase Behavior in Ternary Ethoxylated Alcohol-n-Alkane-Water Mixtures. P. K. KILPATRICK, P. K. KILPATRICK Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this authorC. A. GORMAN, C. A. GORMAN Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this authorH. T. DAVIS, H. T. DAVIS Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this authorL. E. SCRIVEN, L. E. SCRIVEN Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this authorW. G. MILLER, W. G. MILLER Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this author P. K. KILPATRICK, P. K. KILPATRICK Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this authorC. A. GORMAN, C. A. GORMAN Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this authorH. T. DAVIS, H. T. DAVIS Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this authorL. E. SCRIVEN, L. E. SCRIVEN Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this authorW. G. MILLER, W. G. MILLER Dep. Chem. Eng. Mater Sci. Chem., Univ. Minn., Minneapolis, MN 55455,USASearch for more papers by this author First published: February 17, 1987 https://doi.org/10.1002/chin.198707079AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume18, Issue7February 17, 1987 RelatedInformation

Microemulsions employed in enhanced-oil-recovery processes behave in many ways as near-critical mixtures. The similarities suggest that in microemulsions as in mixtures near critical points the component chemical potentials change little with composition in a certain direction in the phase diagram. This is confirmed here for microemulsions for the first time by direct measurement of the chemical potentials of all components in solution. In the microemulsion system tested, the chemical potentials are nearly constant along a path extending from nearly pure oil to midrange to nearly pure water. The persistence of this near-critical behavior over so wide a range of compositions is associated with the peculiar microemulsion properties that are crucial to enhanced oil recovery. In two systems of oil and water with protosurfactant alcohols, the change in chemical potentials with composition, except near critical solution points, is found to be much greater than in a true microemulsion of oil and water with a nonionic surfactant. The experimental technique employed is equilibrium ultracentrifugation, in which concentration gradients in the centrifugal field reveal the mixture equation of state. Strengths and weaknesses of the technique are delineated. Equilibration times are long, but a single equilibrium experiment can give a wealth of data.

Investigations of thin-film effects by means of complete solutions of the augmented Young-Laplace equation are summarized, as are the implications for observable contact angle, certain wettability syndromes, and breakup of nonwetting phase as it is replaced in a porous medium by wetting phase. Apparent contact angle, capillary pressure, and thin-film thickness are found to be interdependent at equilibrium. Contact angle in porous media may depend significantly on pore size, fluid proportions, and filling history. 26 references.