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Solubility of inorganic salts in the mixed systems containing surfactants and sodium tripolyphosphate (STPP) is very important for the production of laundry detergents. In this work we explored the solubility of NaCl, Na2SO4, and Na2CO3 in aqueous surfactant and STPP solutions using an ion selective electrode at 298.15 K. In the experiments, electromotive forces (EMF) for the ternary systems were measured using an ion-meter with a sodium ion-selective composite electrode and the relationship between the solubility and EMF was analyzed by a potentiometric analysis. The proposed method has advantages in avoiding the solid–liquid separation operation and solution supersaturation. The experimental results indicated that the salting-out effect caused by surfactant and STPP can decrease the solubility of sodium salts in the aqueous systems.

Activity coefficients at infinite dilution are reported for ten solutes (heptane, octane, nonane, decane, benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene) in sulfolane at temperatures T = (333.15 to 373.15) K. These data were measured with the help of gas−liquid chromatography (GC) in which sulfolane was used as the stationary phase. The results show good agreement with the activity coefficients at infinite dilution obtained from various methods in the literature. The temperature dependence of the activity coefficients found in the GC experiments could be confirmed using the excess enthalpy data. The present data can be used to determine and compare the selective effect caused by the addition of sulfolane to a given binary mixture in the separation processes such as extractive distillation and solvent extraction. The calculated selectivity suggests that both sulfolane and ionic liquid [HMIM+][BF4-] can act as a good solvent in separating aromatic and aliphatic compounds.

Isobaric vapor−liquid equilibrium data were determined at 101.33 kPa for the binary mixtures of water + sulfolane and water + tetraethylene glycol. Calculations of the nonideality of the vapor phase were made with the second virial coefficients obtained from the Hayden−O'Connell method. The boiling points and vapor-phase compositions reported were well correlated by the Wilson, NRTL, and UNIQUAC models. In addition, the densities of binary mixtures of water + sulfolane, water + tetraethylene glycol, and benzene + tetraethylene glycol were determined over the entire concentration range at 298.15 K and atmospheric pressure by using an oscillating tube densimeter. Excess volumes were calculated for each data point. All mixtures exhibit negative excess volumes with a minimum which occurs at x ≅ 0.5 for the benzene + tetraethylene glycol system; it is shifted toward the water-rich region for the water + sulfolane and water + tetraethylene glycol systems. The experimental excess volumes were correlated using th...

The solubility of sodium dimethyl isophthalate-5-sulfonate in water and in a mixed solvent (water + methanol) containing sodium sulfate was determined from 292.7 K to 360.0 K. Sodium sulfate has a salting out effect on the solubility of sodium dimethyl isophthalate-5-sulfonate in water. The results were correlated by a polynomial equation.