Safranin O

Dark red to brown powder. Soluble in water (30mg/ml) or ethanol. Chemical. CAS: 477-73-6. Formula: C20H19ClN4. MW: 350.84. Synthetic. Redox and adsorption indicator. Employed as a biological stain used in histology, cytology and bacteriology. Biological stain commonly used as a counter stain for gram-negative bacteria in the Gram stain procedure. Has been observed to bind to DNA. In the Flemming triple stain procedure used to stain for chromosomes. In late Palaeozoic pteridosperm cuticles has shown increased contrast, emphasized cutinization differences, and enhanced the three-dimensional morphology of complex epidermal features when compared with other dyes. The compound has also been used with alcian blue in the histochemical study of the distribution and morphometric characteristics of mast cells. Also used to detect mucin and cartilage.