Xylylazo Violet II is primarily used as a metallochromic indicator in analytical chemistry, particularly in complexometric titrations. It is effective in determining metal ions such as calcium, magnesium, and other alkaline earth metals. The compound changes color upon binding to these ions, providing a clear visual endpoint for titration processes. It is also employed in water hardness testing, where it helps quantify the concentration of calcium and magnesium ions in water samples. Additionally, Xylylazo Violet II finds application in biochemical research for studying metal ion interactions with proteins and enzymes, aiding in understanding metal-dependent biological processes. Its stability and sensitivity make it a reliable choice for precise analytical measurements.