Miscibilities of methanol and ethanol with dodecylammonium chloride in the adsorbed film and micelle

The surface tension of the aqueous solutions of methanoldodecylammonium chloride (DAC) and ethanol-DAC mixtures has been measured as a function of the total molality of the mixture m̂ and the mole fraction of DAC X̂₂ in the mixture at 298.15 K under atmospheric pressure. The compositions of the adsorbed film at 50, 40, and 30 mNm'^-1, and that of the micelle at the critical micelle concentration (CMC) have been evaluated by applying the thermodynamic equations derived previously and shown in the form of phase diagrams of adsorption and micelle formation. It has been found that (i) methanol is hardly miscible in the adsorbed film and micelle, and (ii) ethanol molecules are very slightly incorporated into adsorbed film of DAC at high-surface tension and into the micelle, although hardly miscible in the adsorbed film at low-surface tension. By comparing the corresponding phase diagrams of ethanol-2-(octylsulfinyl)ethanol (OSE) mixture, furthermore, it has been shown that there exists a difference in the miscibility of ethanol between DAC and OSE.