The adsorption of dioctadecyl ether was studied at hexane/water interface, as functions of temperature, pres?sure, and mole fraction of dioctadecyl ether in hexane. The phase transition between expanded and condensed films was observed with decreasing temperature and increasing pressure and concentration. The thermodynamic quan?tities associated with the adsorption such as entropy, volume, and energy change were evaluated and comparison was made with the adsorbed films of 1-octadecanol at the same interface in which phase transition takes place. It is found that the dioctadecyl ether shows small negative discontinuous changes of the thermodynamic quantities with the transition from the expanded to the condensed films.
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