6-[[4-[[4-[(4-Ethoxy-3-sulfophenyl)methylamino]phenyl]methylene]-4,5-dihydro-3-methyl-5-oxo-1H-pyrazol]-1-yl]-2-naphthalenesulfonic acid

6-[4-[[4-[(4-ethoxy-3-sulphophenyl)methylamino]phenyl]methylene]-4,5-dihydro-3-methyl-5-oxo-1H-pyrazol-1-yl]naphthalene-2-sulphonic acid