T 1645 (OTTO) Thionin Cas 78338-22-4 - used for biological staining. Thionine can also be used in place of Schiff reagent in quantitative Feulgen staining of DNA. It can also be used to mediate electron transfer in microbial fuel cells. It is also employed as a general nuclear stain for chromatin and mucin; for staining Nissl granules by end-point buffering and for showing malignant cells in frozen biopsy sections; and as a stain for semi-thin sections of plant material for light microscopy.