Disodium-4-nitro-2-sulfobenzoate (NSBNa2) and 4-amino-2-sulfo-benzoic acid (ASB) are important intermediates in fine chemical industries. In this study, the solubilities of NSBNa2 and ASB in sulfuric acid aqueous solutions were measured to provide important data for their production and separation. The measurement was performed at temperatures from 277.1 to 347.9 K under atmospheric pressure by a dynamic method. The solubilities of NSBNa2 and ASB were found to be increased with temperature at fixed concentrations of sulfuric acid. While, their solubilities decreased with the concentration increasing of sulfuric acid. The experimental data were then correlated with the modified Apelblat model, and the root-mean-square deviations ranged from 0.77 to 1.26 K. The calculated results show good agreement with the experimental data. Based on the solubility data, improved separation processes for NSBNa2 and ASB were also proposed for higher recycle yields.