Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Cloud point (CP) data have been acquired for two anionic surfactants, namely, tetra-n-butyl ammonium dodecylsulfate (TBADS) and tetra-n-butylammonium dodecylbenzenesulfonate (TBADBS) with and without salts (Ca(NO3)2 and Al(NO3)3). The energetics of clouding process, standard Gibbs free energy change (AGdeg c), standard enthalpy change (AHdeg c), and standard entropy (ASdeg c) were evaluated. The release of solvated water from the clouding component causes the phase separation. Hence CP was taken as the limit of its solubility. The AGdeg c for all of the systems with and without inorganic salts is found to be negative. However, both AHdeg c and ASdeg c are positive and negative depending upon concentration and charge on the counterion. The results are discussed in the light of exchange of counterions (TBA+ by Ca2+ or Al3+) and formation of bridges through displaced TBA+ among the anionic micelles present in the solution.