7-[[4,5-dihydro-3-methyl-5-oxo-1-[4-[[2-(sulphooxy)ethyl]sulphonyl]phenyl]-1H-pyrazol-4-yl]azo]naphthalene-1,3-disulphonic acid, sodium salt

7-[[[4,5-Dihydro-3-methyl-5-oxo-1-[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]-1H-pyrazole]-4-yl]azo]-1,3-naphthalenedisulfonic acid/sodium,(1:x) salt