Fuchsine

Fuchsine or rosaniline hydrochloride is a magenta dye with chemical formula C20H19N3·HCl. There are other similar chemical formulations of products sold as fuchsine, and several dozen other synonyms of this molecule.

It becomes magenta when dissolved in water; as a solid, it forms dark green crystals. As well as dying textiles, fuchsine is used to stain bacteria and sometimes as a disinfectant.

History
Fuchsine, named by its original manufacturer Renard frères et Franc, is usually cited with one of two etymologies: from the color of the flowers of the plant genus Fuchsia, named in honor of botanist Leonhart Fuchs, or as the German translation Fuchs of the French name Renard, which means fox. An 1861 article in Répertoire de Pharmacie said that the name was chosen for both reasons.

Acid fuchsine
Acid fuchsine is a mixture of homologues of basic fuchsin, modified by addition of sulfonic groups. While this yields twelve possible isomers, all of them are satisfactory despite slight differences in their properties.

Basic fuchsine
Basic fuchsine is a mixture of rosanilin, pararosanilin, and Magenta II. Formulations usable for making of Schiff reagent must have high content of pararosanilin. The actual composition of basic fuchsine tends to somewhat vary by vendor and batch, making the batches differently suitable for different purposes.

In solution with phenol as an accentuator it is called carbol fuchsin and is used for the staining of the bacterium which cause tuberculosis.