Solubility of Sodium Naphthalene Disulfonate in Aqueous Solutions of Sulfuric Acid

The solubilities of sodium 2,6-naphthalene disulfonate and sodium 2,7-naphthalene disulfonate in aqueous solutions of sulfuric acid were measured in the temperature range from (283.15 to 333.15) K by a steady-state method. The solubility of sodium 2,6-naphthalene disulfonate or sodium 2,7-naphthalene disulfonate increases with the increase in temperature from (283.15 to 333.15) K. With the increase in sulfuric acid concentrations, the solubilities of sodium 2,6-naphthalene disulfonate and sodium 2,7-naphthalene disulfonate decrease. At the same temperature and in the same composition of sulfuric acid + water solvent mixtures, the solubility of sodium 2,7-naphthalene disulfonate is larger than that of sodium 2,6-naphthalene disulfonate. Results of these measurements were correlated by a modified Apelblat equation.