4-[(5-cyano-1-ethyl-1,6-dihydro-2-hydroxy-4-methyl-6-oxo-3-pyridyl)azo]benzene-1,3-disulphonic acid

4-[[(5-Cyano-1-ethyl-1,6-dihydro-2-hydroxy-4-methyl-6-oxopyridin)-3-yl]azo]-1,3-benzenedisulfonic acid