1-(3-Sulfonatopropyl)-2-[2-[[1-[3-(sodiosulfo)propyl]naphtho[1,2-d]thiazol-2(1H)-ylidene]methyl]-1-butenyl]naphtho[1,2-d]thiazol-1-ium

hydrogen -1-(3-sulphonatopropyl)-2-[2-[[1-(3-sulphonatopropyl)naphtho[1,2-d]thiazol-2(1H)-ylidene]methyl]-1-butenyl]naphtho[1,2-d]thiazolium, sodium salt