Safranin is also known by the names of safranin O, safranin Y, safranin T, safranin A, basic red 2, gossypimine and cotton red. It consists of dark red crystals available as a dimethyl or trimethyl derivatives; both show the same staining properties. Commercial safranin stains may contain either of these two or a combination of both derivatives.
Gram staining involves the application of crystal violet stain to bacterial cells followed by the addition of an iodine solution. When a slide thus treated is washed with a de-staining liquid, certain cells undergo de-colorization whereas others do not. When safranin is added to such specimens, it acts as a counter-stain. The decolorized cells take it up to show a red color; the cells that resisted de-colorization do not take it up and display the deep blue color of the initial crystal violet stain. Cells that take the red color are said to be gram negative, whereas those that remain blue are gram positive.
The major use of safranin is as a counter-stain in gram staining. Besides this, it also finds use in histological and cytological staining procedures to stain cellular nuclei red. It is used as a component in the Flemming triple stain used to stain chromosomes. Safranin has also been used in the staining of cartilage, where the nuclei appear red against a pink background.
Safranin is not explosive or inflammable under ordinary laboratory conditions. However, it is important to handle safranin solutions in the laboratory carefully. Avoid contact with skin and eyes because it can cause irritation of both. Never draw the solution by sucking through a pipette; use a dropper to pick up the stain because it is dangerous to swallow, as it irritates the upper respiratory tract and its mucous membranes.