Acid Fuchsin Solution is a red-magenta staining solution containing Acid Fuchsin dye, a sodium sulfonate derivative of basic fuchsine, which is used in histology and microbiology for staining tissue, bacteria, and chromosomes. It is a component of trichrome stains, such as Masson’s trichrome, where it stains muscle fibers red, and is also used in analytical chemistry as a pH indicator.