Eosin B is a form of eosin which is a dye compound. There is another form of eosin B dye and its chemical name is 4, 5-dibromo-2, 7dinitro- fluorescein or 4â²,5â²-dibromo-2â²,7â²-dinitro-3-oxo-3Hspiro[2-benzofuran-1,9â²-xanthene]-3â²,6â² diolate. This last form of eosin B is an organic laser dye.