Used as a catalyst in organic synthesis, particularly in esterification, etherification, and transesterification reactions due to its strong acidic properties. Commonly employed in the production of dyes, pharmaceuticals, fragrances, resins, lubricants, and coatings where a stable, water-soluble acid is required. Its dihydrate form enhances handling safety and solubility in polar solvents, making it suitable for aqueous reaction systems. Also utilized in resin modification, as a proton source in chemical transformations, and as a starting material for producing other sulfonic compounds used in the detergent and surfactant industries.