SMILES: C1=CC2=C(C=C1S(=O)(=O)[O-])C(=C(N2)C3=NC4=C(C3=O)C=C(C=C4)S(=O)(=O)[O-])O.[Na+].[Na+]
Description: The molecule is an organic sodium salt resulting from the formal condensation of indigo carmine (acid form) with two equivalents of sodium hydroxide. It is an indicator at pH 11.5-14, changing from blue to yellow. It has a role as a food colouring, a histological dye and a two-colour indicator. It contains an indigo carmine(2-).