Sodium 2,3-dihydroxynaphthalene-6-sulfonate, also known as sodium dihydroxynaphthalene sulfonate, is a chemical compound with the molecular formula C10H7NaO5S. It is a water-soluble solid that is commonly used in analytical chemistry and as a chemical reagent. This compound is often utilized as a developer in colorimetric assays for the determination of various substances, including phenols, amino acids, and other organic compounds.