In detail, eosin is a derivative of fluorescein, a molecule with green fluorescence used to produce other dyes - such as, precisely, eosin - as a pH indicator and even for the execution of fluorescence diagnostic tests. .
However, from a chemical point of view, eosin proper - also known as common eosin or eosin Y - is a tetrabromic derivative of fluorescein which occurs as a red crystalline powder, soluble in water and alcohol, with green fluorescence.
There is also another form of eosin, known in common language as eosin scarlet or eosin B. It is a brown crystalline powder, soluble in water, whose uses are similar to those of common eosin. From the chemical point of view, it differs from the latter by the presence of two nitric groups in place of two of the four bromine atoms present in the Y form. The latter, however, is the most exploited form of eosin.
In addition to its use as a dye, eosin is also used in the medical-pharmaceutical field by virtue of its disinfectant action for the skin which is associated with its ability to promote healing when it is injured, abraded or burned.
In this article, only the use of eosin in the medical field will be considered.
