Safranin O is a mixture of the two compounds shown, according to Conn. Aldrich and Gurr give only the dimethyl compound.
Safranin O is commonly used for staining Gram negative bacteria red in smears to contrast with the blue Gram positive organisms. For tissue sections it is useful as a red nuclear counterstain, and was popular at one time for staining cartilage metachromatically yellow, against red nuclei on a pink background.
R. D. Lillie.
Conn's Biological Stains
Williams & Wilkins, Baltimore, MD., U.S.A.
Edward Gurr, (1971)
Synthetic dyes in biology, medicine and chemistry
Academic Press, London, England.
Aldrich chemical catalogue, 1992
Aldrich Chemical Company, Milwaukee, WI, USA.