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A Head-Space Method for Measuring Activity Coefficients, Partition Coefficients, and Solubilities of Hydrocarbons in
Stanley P Wasik1, Frederick P Schwarz1, Yadu B Tewari1
1National Bureau of Standards, Gaithersburg, MD 20899.
Abstract:
An apparatus is described which measures the equilibrium distribution of a hydrocarbon between a gas and aqueous phase. Soluble hydrocarbons are extracted from an aqueous salt solution by very small bubbles of hydrogen generated electrolytically from a gold electrode located at the bottom of a cylindrical cell. The partition coefficient is determined from the volume of the aqueous solution and the solute concentration in the head-space after a measured volume of hydrogen has bubbled through the cell. The concentration of the solute in the head-space is measured by gas chromatography. The observed distribution is supplemented by vapor pressure and molar volume data and can be used to calculate the solubility and the activity coefficient of the solute in the aqueous phase. The partition coefficient, activity coefficient, and solubility for 18 alkylbenzenes in aqueous 0.5 M NaCl at 25 °C were measured by this method.
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