Mercurochrome is infrequently substituted for Eosin Y ws. It has a similar colour, but is darker and recorded better on early colour films. In the past it was used to mark tissue margins and faces for orientation, but tattoo inks are superior for this. It was also commonly used as an antiseptic. Due to the mercury content and its consequent toxicity, it should not be used.

Two different formulas have been given. The one by Merck is the more accepted.

Compare the structural formulae of some eosin homologues.