Used primarily as a reagent in analytical chemistry for detecting and measuring trace amounts of oxidants, such as chlorine, in water. It serves as a key component in colorimetric tests, where it reacts with oxidants to produce a distinct color change, enabling easy visual or spectrophotometric quantification. Additionally, it finds application in the synthesis of dyes and pigments, contributing to the production of various colored materials. In biological research, it is employed as a staining agent for visualizing certain cellular structures under a microscope. Its role in these diverse fields highlights its importance in both industrial and scientific applications.