tetrasodium 2,2'-[iminobis[(1-hydroxy-3-sulphonato-6,2-naphthalenediyl)azo-3,1-phenyleneimino]]bis(2-oxoacetate)

2,2'-[Iminobis[(1-hydroxy-3-sodiosulfo-6,2-naphthalenediyl)azo-3,1-phenyleneimino]]bis[2-oxoacetic acid sodium] salt