Eriochrome Black A is widely used as a metallochromic indicator in complexometric titrations, particularly for determining the concentration of metal ions such as calcium, magnesium, and other divalent cations. It forms distinct color changes when it binds to these metal ions, making it valuable in water hardness testing and analytical chemistry. Additionally, it is employed in dyeing processes for textiles, where it acts as a mordant dye to enhance color fastness on fabrics. Its ability to chelate metal ions also makes it useful in certain industrial applications, including metal ion detection and separation processes.