Xylenol Orange sodium salt is widely used as a metallochromic indicator in analytical chemistry, particularly in complexometric titrations. It is effective in detecting metal ions such as zinc, lead, and rare earth elements by forming colored complexes, which helps in determining endpoint during titrations. Additionally, it is employed in biochemical research for staining and visualizing calcium deposits in tissues, aiding in studies related to bone metabolism and mineralization. Its ability to bind selectively to metal ions also makes it useful in environmental testing for monitoring metal contamination in water and soil samples.