Solubility determination and thermodynamic modeling of sodium 1-naphthalenesulfonate and sodium 2-naphthalenesulfonate in six organic solvents from TÂ =Â (278.15 to 323.15) K and mixing properties of solutions

The solubility of sodium 1-naphthalenesulfonate and sodium 2-naphthalenesulfonate in pure organic solvents of acetone, 1,4-dioxane, cyclohexanone, ethanol, ethyl acetate and isopropanol were measured by using the isothermal saturation method at temperature ranging from (278.15 to 323.15) K under 101.3 kPa. The mole fraction solubility of sodium 1-naphthalenesulfonate and sodium 2-naphthalenesulfonate in the selected pure solvents increased with the increase in temperature. The maximum mole fraction solubility of sodium 1-naphthalenesulfonate was observed in ethanol (2.767 × 10− 3 at 323.15 K), followed by that in 1,4-dioxane (2.028 × 10− 3 at 323.15 K), cyclohexanone (1.522 × 10− 3 at 323.15 K), isopropanol (1.094 × 10− 3 at 323.15 K), acetone (5.997 × 10− 4 at 308.15 K) and ethyl acetate (3.111 × 10− 4 at 323.15 K); For sodium 2-naphthalenesulfonate + solvents systems, the maximum mole fraction solubility was observed in ethanol (1.178 × 10− 3 at 323.15 K), followed by that in 1,4-dioxane (1.027 × 10− 3 at 323.15 K), ethyl acetate (6.197 × 10− 4 at 323.15 K), cyclohexanone (3.233 × 10− 4 at 323.15 K), isopropanol (1.058 × 10− 4 at 323.15 K) and acetone (9.683 × 10− 5 at 323.15 K). The measured solubility data were correlated and calculated by using the modified Apelblat equation, λh equation and NRTL model. The calculated solubilities agreed better with the experimental values by using the modified Apelblat equation than the other two models. Moreover, the mixing properties including the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (γ1∞) and reduced excess enthalpy (H1E , ∞) were calculated by NRTL model.