Arsenazo I is primarily used as a chromogenic reagent in analytical chemistry for the detection and quantification of metal ions, particularly thorium and uranium. It forms highly colored complexes with these ions, allowing for sensitive spectrophotometric analysis. The reagent is also employed in environmental monitoring to assess the presence of heavy metals in water and soil samples. Additionally, Arsenazo I finds application in biochemical research for studying metal-protein interactions due to its selective binding properties. Its ability to provide clear visual and measurable changes makes it a valuable tool in both qualitative and quantitative analyses.