Used as a colorimetric reagent for the detection and determination of metal ions, particularly in analytical chemistry. It forms stable colored complexes with certain transition metals, allowing for visual or spectrophotometric analysis. Commonly employed in test kits and qualitative analysis due to its distinct color change upon complexation. Also utilized in the synthesis of dyes and pigments where a strong chromophore is required. Its high sensitivity and selectivity make it suitable for environmental monitoring and industrial quality control applications.