Bathocuproine disulfonate disodium (BCS) is an organic compound used as a highly sensitive colorimetric reagent for copper ions in biochemical and analytical applications. It has a bright yellow color and absorbs light at specific wavelengths, so it can be used to detect and quantify trace copper. In biochemical applications, BCS is commonly used to study the role of copper ions in various biological processes. Copper is an essential nutrient for many organisms, but it can also be toxic in high concentrations, so accurate measurement of copper levels is important to understand its impact on living systems. In terms of analysis, BCS is often used in environmental monitoring and water quality testing to detect copper pollution. It can detect copper even at very low concentrations, making it an invaluable tool for identifying potential sources of pollution and assessing the impact of industrial activities on aquatic ecosystems.