Used primarily as a reagent in organic synthesis, particularly in the preparation of azo dyes. It serves as a key intermediate in coupling reactions to produce vibrant and stable dyes for textiles, inks, and pigments. Additionally, it is employed in biochemical research for labeling and detecting proteins or nucleic acids due to its ability to form covalent bonds with specific functional groups. In analytical chemistry, it is utilized for colorimetric assays to quantify substances based on color changes. Its sulfonic acid group also makes it useful in modifying surfaces to enhance hydrophilicity or reactivity in material science applications.