Synonyms: 3H-Indolium,2-[2-[3-[2-[1,3-dihydro-3,3-dimethyl-1-(4-sulfobutyl)-2H-indol-2-ylidene]ethylidene]-2-[(4-isothiocyanatophenyl)thio]-1-cyclohexen-1-yl]ethenyl]-3,3-dimethyl-1-(4-sulfobutyl)-,inner salt, sodium salt (1:1)