The laser Raman scattering by potassium n-alkyl carboxylates and sodium n-alkyl sulfates was measured in the solid state and aqueous solutions, and the concentration dependence of molecular conformations of these molecules was studied. For aqueous solutions of potassium n-hexanoate and potassium n-pentanoate, the Raman intensities of the accordion vibrations of the all-trans form relative to the skeletal deformation vibrations of the gauche isomers were found to increase with an increase in the concentration. This intensity change is remarkable at the critical micelle concentration. A concentration dependence of the intensity of the Raman lines was also observed in the frequency region of 1600–600 cm−1. These observations revealed that the percentage of the all-trans form of the surfactant molecules increases with an increase in the concentration above the critical micelle concentration.
The Raman spectra were measured for sodium alkyl sulfates and potassium aliphatic carboxylates in the solid state and aqueous solutions. Vibrational assignments of Raman lines were made, and characteristic Raman lines of the alkyl sulfate ion were identified. The ethyl sulfate ion in the aqueous solution was found to exist predominantly as the trans form about the CH2–O bond. For higher alkyl sulfate ions in aqueous solutions, Raman lines due to rotational isomers with gauche CH2–CH2 bonds were observed. Longitudinal accordion frequencies of the solid state and aqueous solutions were compared in order to discuss the conformations of hydrocarbon chains in solution.
The evaporation—condensation coefficient for very small droplets is derived in the form α(a) =δ·φ(a), where δ is the free-angle ratio and φ(a) is the size coefficient which is expressed in terms of the droplet radius a, the absolute temperature, and other characteristic variables of the liquid phase and the gas—liquid interface. With the inclusion of α(a) into the rate equations of Fuchs and of Monchick and Reiss, the rate of evaporation per unit area increases with decreasing droplet radius, reaches a maximum at droplet radii ranging between 1 and 0.01 μ, then decreases to zero as the radius approaches zero. Numerical results were obtained for H2O, He, and Hg at their respective freezing and boiling points.
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