Disodium phthalate is primarily used as a buffering agent in various industrial and laboratory applications. It helps maintain a stable pH level in solutions, making it valuable in chemical processes where pH control is critical. In the textile industry, it is employed as a dyeing auxiliary to improve the color fastness and uniformity of dyes on fabrics. Additionally, it finds use in the production of adhesives and coatings, where it acts as a stabilizer to enhance product performance. In analytical chemistry, it serves as a reagent for calibrating instruments and preparing standard solutions. Its ability to chelate metal ions also makes it useful in water treatment processes to prevent scaling and corrosion.