Apparent molar volumes
Vφ,
apparent molar heat capacities Cp, φ, and relative apparent molar enthalpies
Lφ of the mixed solute {di-2-ethylhexyl sodium sulfosuccinate (Aerosol OT, or AOT)+r·H
2O} in cyclohexane were determined over the molality range of 0.0002 to 1mol kg
-1 at 298.15K. The heats of dilution were measured by using a newly constructed flow-calorimeter. The excess enthalpies for the systems (benzene+cyclohexane) and (chlorobenzene+toluene) at 298.15K were also measured to test the operating technique for the calorimeter. In the system without adding water (r=0) the enthalpy of dilution changes from endotherm to exotherm at about 0.2mol kg
-1, and the change in
Cp, φ with molality is monotonous. In the systems with r≥5 a sharp peak appears at
m=0.001mol kg
-1 in
Cp, φ and the enthalpy of dilution increases very sharply at
m < 0.01mol kg
-1. We concluded that the intermolecular interaction of AOT in cyclohexane is moderate, and no micelles are formed. In the systems with r≥5 a transition occurs at
m=0.001mol kg
-1 and W/O microemultion is formed.
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