How many types of eosin are there?
First we should define what is meant by the name eosin. Quite obviously at its simplest it refers to the dyes actually named eosin, particularly eosin Y ws, which is nearly always what is meant, but also to eosin B and ethyl eosin. That is, however, a very restrictive use of the word. There are other dyes which are very close chemical and structural relatives of the three mentioned above. The term eosins (plural) is sometimes used as a group name to refer to all of these dyes, instead of identifying individual compounds. They are all halogenated derivatives of fluorescien and are acid dyes shaded pink to red.
