Used in complexometric titrations to detect the endpoint when determining metal ions such as copper, nickel, and cobalt. It forms a stable colored complex with these metals, typically red or violet, which changes to a clear or blue color when the metal ions are chelated by EDTA during titration. Particularly effective in non-aqueous or slightly acidic to neutral conditions where other indicators may not perform well. Commonly used in pharmaceutical analysis and quality control of metal-containing compounds.