Temperature and sodium chloride effects on the solubility of anthracene in water

The solubility of anthracene was measured in pure water and in sodium chloride aqueous solution (salt concentration, m/mol · kg−1 = 0.1006, 0.5056, and 0.6082) at temperatures between (278 and 333) K. Solubility of anthracene in pure water agrees fairly well with values reported in earlier similar studies. Solubility of anthracene in sodium chloride aqueous solutions ranged from (6 · 10−8 to 143 · 10−8) mol · kg−1. Sodium chloride had a salting-out effect on the solubility of anthracene. The salting-out coefficients did not vary significantly with temperature over the range studied. The average salting-out coefficient for anthracene was 0.256 kg · mol−1.The standard molar Gibbs free energies, ΔtrG°, enthalpies, ΔtrH°, and entropies, ΔtrS°, for the transfer of anthracene from pure water to sodium chloride aqueous solutions were also estimated. Most of the estimated ΔtrG° values were positive [(20 to 1230) J · mol−1]. The analysis of the thermodynamic parameters shows that the transfer of anthracene from pure water to sodium chloride aqueous solution is thermodynamically unfavorable, and that this unfavorable condition is caused by a decrease in entropy.