Thermodynamic study on the interface formation of water-long-chain alcohol systems

The interfacial tensions of the water-decyl alcohol (DEA), -undecyl alcohol (UNA), and -dodecyl alcohol (DOA) systems were measured as a function of temperature and pressure. The thermodynamic quantities of interface formation were evaluated from the experimental results; the entropy, volume, and energy were found to have negative values and change discontinuously at the break point on the interfacial tension vs temperature and pressure curves. These results were discussed in terms of the orientation of alcohol molecules at the interface caused by the interaction between alcohol and water molecules. Further, it was suggested that the phase transition takes place between the expanded and condensed states at the interface.