Solution properties of some gaseous hydrocarbons in water-alkanol mixtures
The solubility of several hydrocarbon gases in water and in aqueous alcohol solvents has been measured in the temperature range 4-61 °C at a total pressure of one atmosphere, by a physical method based on the flowing film technique. Using standard procedures, ΔG ΔH and ΔS of solution have been evaluated and expressed as functions of temperature and solvent composition. The observed variations in these functions and their dependence on temperature and alcohol concentration are then related to current theories of water structure also discussed here but with particular reference to hydrophobic interactions in the solution. It is shown that the extent of these interactions can be observed in the isotherms of ΔH and ΔS at low concentrations of alcohol and a numerical method was used to estimate the magnitude of the hydrophobic contribution to the observed values of the functions themselves. The changes in these functions are then related to the sizes and shapes of the chosen solute molecules to provide a possible structural interpretation of the hydrophobic effect consistent with the observed experimental results.
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