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A molecular-thermodynamic model has been established for the solubilities of gases in non-polar and polar solvents and in aqueous solutions of e~ectrolytes. To obtain an expression for the Helmholz energy of the mixture~ the pure components are first mixed isothermally to form an ideal gas mixture. Then each particle in the mixture is inflated into a hard sphere. Finally, all particles are charged with an appropriate potential to form a real liquid mixture; this charging step is based on an ordered first coordination shell and a random mixture beyond that first shell. This model agrees well with computer-simulation data. Calculated and observed Henry's constants are in good agreement over a wide range of temperature for various gases in benzene, cyclohexane, n-hexane, hexadecane and water, and in aqueous solutions of NaCI and KOH.

Abstract--Ludox HS Sit 2 sols at high concentrations show a peak in small angle x-ray scattering (SAXS) reminiscent to a "structure." The appearance of such a peak was found to depend crucially on the thickness of the sample cell used for SAXS measurements. The thinner the cell used, the more prominent the peak. When the thickness was larger than 2 rnm, it was no longer observable. When sols were treated with activated charcoal powders (in order to remove a surfactant) the peak became less prominent.For the cases where clear features for structure were absent (thick sample regime), the Smoluchowski scheme was utilized to study the nature of sols. Namely, the distribution of the Smoluchowski species were estimated by numerically calculating the size distribution of particles directly from SAXS data. The distribution was found basically bimodal, and the main distribution peak, particularly for dilute sols (less than 5 wt%), was consistent with primary particles of Sit2. The second distribution peak was strongly dependent on the concentration of Sit2 particles. The observed trend was that the higher the concentration of Sit 2 particles, the more prominent the second distribution peak and the locus of the maximum tended to move toward a smaller value in diameter. This behavior of the second distribution peak of the Smoluchowski species is no doubt a manifestation of the interparticle correlation. The observation of such behavior may provide a convenient means to characterize sols with interparticle correlation. This method was also applied for characterizing gels formed when the pH values were altered.

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