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Journal ArticleDOI

The surface tension of sodium dodecylsulfate solutions and the phase separation model of micelle formation

01 Mar 1966-Journal of Colloid and Interface Science (Academic Press)-Vol. 21, Iss: 3, pp 331-347
TL;DR: In this article, a modified equilibrium Wilhelmy method was used to obtain accurate and precise surface tension measurements of surfactant solutions above the c.m.c. This finding places a definite limit upon the validity of the approximation represented by the phase separation theory of micelle formation.
About: This article is published in Journal of Colloid and Interface Science.The article was published on 1966-03-01. It has received 310 citations till now. The article focuses on the topics: Surface tension & Micelle.
Citations
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Journal ArticleDOI
TL;DR: Influence of different parameters such as molecular structure, temperature, salt concentration, and salt concentration that are very important in surfactant adsorption are reviewed here.

901 citations

Journal ArticleDOI
TL;DR: In this paper, a review of equilibrium and dynamic aspects of surface tension and adsorption, primarily of single nonmicellar or premiceller surfactants at the air/water interface, is presented.

675 citations

Journal ArticleDOI
TL;DR: In this article, the specular reflection of neutrons has been applied to the study of surface and interfaces, and a range of recent experimental results in surface chemistry, solid films and surface magnetism are discussed.
Abstract: The application of the specular reflection of neutrons to the study of surface and interfaces is described. The theoretical and experimental background to the technique is presented. A range of recent experimental results in surface chemistry, solid films and surface magnetism is discussed. In surface chemistry the results include adsorption of surfactants at the air-solution interface, insoluble monolayers and polymers at the air-liquid interface, soap films and adsorption at the liquid-solid and liquid-liquid interfaces. In solid films results on Langmuir-Blodgett films, hard carbon films, polymer films and some semiconductor layers are discussed. In surface magnetism experimental data which illustrate the nature of magnetism in magnetic multilayers and ferromagnetic films, and which describe flux penetration in superconductors, are presented.

555 citations

Journal ArticleDOI
TL;DR: The phase behavior of several medium-chain and long-chain fatty acids in water was examined as a function of the ionization state of the carboxyl group to provide insights into the physical states of fatty acid in biological systems.
Abstract: The phase behavior of several medium-chain (10- and 12-carbon) and long-chain (18-carbon) fatty acids in water was examined as a function of the ionization state of the carboxyl group. Equilibrium titration curves were generated above and below fatty acid and acid-soap chain melting temperatures and critical micelle concentrations, and the phases formed were characterized by X-ray diffraction, 13C NMR spectroscopy, and phase-contrast and polarized light microscopy. The resulting titration curves were divided into five regions: (i) at pH values less than 7, a two-phase region containing oil or fatty acid crystals and an aqueous phase; (ii) at pH approximately 7, a three-phase region containing oil, lamellar, and aqueous (or fatty acid crystals, 1:1 acid-soap crystals, and aqueous) phases; (iii) between pH 7 and 9, a two-phase region containing a lamellar fatty acid/soap (or crystalline 1:1 acid-soap) phase in an aqueous phase; (iv) at pH approximately 9, a three-phase region containing lamellar fatty acid-soap (or crystalline 1:1 acid-soap), micellar, and aqueous phases; and (v) at pH values greater than 9, a two-phase region containing micellar and aqueous phases. Interpretation of the results using the Gibbs phase rule indicated that, for oleic acid/potassium oleate, the composition of the lamellar fatty acid/soap phase varied from approximately 1:1 to 1:3 un-ionized to ionized fatty acid species. In addition, constant pH regions observed in titration curves were a result of thermodynamic invariance (zero degrees of freedom) rather than buffering capacity. The results provide insights into the physical states of fatty acids in biological systems.(ABSTRACT TRUNCATED AT 250 WORDS)

407 citations

References
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Journal ArticleDOI
P. Debye1
TL;DR: Soap solutions exhibit even lower osmotic activity than would be predicted if one assumed that soap existed in solution as simple undissociated molecules, and cryoscopic evidence of micelle formation in aqueous solutions of severa1 non-ionic detergents is obtained.
Abstract: Soap solutions exhibit even lower osmotic activity than would be predicted if one assumed that soap existed in solution as simple undissociated molecules. Soap solutions alço conduct the electric current far better than would be expected from the observed osmotic effects. Attempting to explain these anomalies, McBain,' in 1913, suggested that the fatty soap ions aggregated in solution. Such colloidal aggregations of ions, which were termed micelles, would explain the low osmotic activity and relatively high conductivity of soap solutions. Since 1913, investigators have shown considerable interest in the determination of the size and shape of the micelle. McBainP proposed two different rnicelle species, which he said could coexist in solution: one a small, spherical, hydrated, ionic micelle, and the other a large, larnellar, weakly conducting micelle. While agreeing with McBain that the behavior of soap solutions pointed to the existence of micelles, Hartleya took the view that only the small spherical micelle was feasièle. On the basis of geometrical considerations, Hartley4 calculated that the micelle of a 16 carbon soap consisted of approximately 50 cetyl chains. He and Runnicles5 carried out diffusion experiments with cetyl pyridinium chloride and calculated from their results that the micelle of this soap contained about 70 paraffin chains. Ultracentrifuge and diffusion measurements by Miller and Andersson' on Duponal (sodium salts of sulfated aliphatic alcohols of chain length C S to C,,) led to a molecular weight of 12,500 for the mixed micelle. Hakala' has made diff usion measurements on sodium dodecyl sulfate solutions. If a spherical model for the micelle is assumed, the introdgction of his results into the Stokes-Einstein equation gives a value of 23.6 A for the radius. A molecular weight of about 25,000 (87 paraffin chains per micelle) is obtained from this value of the radius if a density equal to that of dodecane is taken. Vetter' studied the sodium salt of sulfonated di (2-hexyl) succinate, known commercially as Aerosol MA, and from density, viscosity, and diffusion data calculated an aggregation number of 24 for the micelle. Gonick and McBain' obtained cryoscopic evidence of micelle formation in aqueous solutions of severa1 non-ionic detergents. Assuming ideal behavior, their data indicate that a micelle consists of no more than 7 detergent molecules.

190 citations

Journal ArticleDOI
TL;DR: In this article, specific conductivities of aqueous solutions of sodium dodecyl sulfate, sodium decyl sulphate, and sodium octyl sulphates were measured over concentration ranges about the respective CMCs and at temperatures from 10° to 55 °C.
Abstract: Specific conductivities of aqueous solutions of sodium dodecyl sulphate, sodium decyl sulphate, and sodium octyl sulphate were measured over concentration ranges about the respective CMCs and at temperatures from 10° to 55 °C. Values of the increase in heat content associated with micelle formation are estimated from the temperature variation of the CMC and the relation of these results to the theory of micelle formation is considered.

184 citations