6-acetamido-4-hydroxy-3-[[4-[[2-(phosphonooxy)ethyl]sulphonyl]phenyl]azo]naphthalene-2-sulphonic acid, sodium salt

6-(Acetylamino)-4-hydroxy-3-[[4-[[2-(phosphonooxy)ethyl]sulfonyl]phenyl]azo]-2-naphthalenesulfonic acid/sodium,(1:x) salt