In the title compound, C(14)H(10)O(6)S(2), the dihedral angle between the planes of the two phenyl-ene rings is 55.9 (1)°. Both hydr-oxy groups form intra-molecular hydrogen bonds; however, one of them also engages in inter-molecular hydrogen bonding. In the crystal, mol-ecules are connected into helical chains by O-H⋯O hydrogen bonds. The crystal studied was an inversion twin with a domain ratio of 0.51 (13):0.49 (13).