Bleaching chemicals are oxidizing or reducing agents used to remove or decolorize natural pigments, stains, and impurities from materials. In industrial applications, their primary function is to achieve a high degree of whiteness and brightness. The most common and powerful bleaching agents are oxidizing agents, which break the chemical bonds in colored molecules (chromophores). The dominant chemicals vary by industry: in the pulp and paper industry, chlorine dioxide (ClO₂) is the modern standard for elemental chlorine-free (ECF) bleaching due to its selectivity and minimal environmental impact compared to elemental chlorine. Hydrogen peroxide (H₂O₂) and sodium hydrosulfite are also widely used. In the textile industry for cotton and other fibers, hydrogen peroxide is the most common agent, often applied in a controlled, hot alkaline bath.