o-Tolidine is primarily used as a chemical intermediate in the production of dyes and pigments, particularly for coloring textiles, paper, and leather. It is also employed in the synthesis of certain polymers and resins, which are utilized in various industrial applications. In analytical chemistry, o-Tolidine serves as a reagent for detecting trace amounts of chlorine in water and for occult blood in clinical samples, making it valuable for water quality testing and medical diagnostics. Additionally, it has been used in the development of certain types of adhesives and coatings. However, due to its potential health risks, including carcinogenicity, its use is regulated and often replaced with safer alternatives in many applications.