Used as an intermediate in the synthesis of dyes and pigments, particularly in the production of sulfur dyes for cotton and other cellulosic fibers. It acts as a reducing agent in dyeing processes, helping to convert insoluble dyes into water-soluble forms for better fabric penetration. Also employed in organic synthesis for chlorination reactions and in the preparation of sulfones and other sulfur-containing compounds. Its reactivity makes it useful in polymer chemistry as a catalyst or modifier in certain chain reactions.