2,2'-Dinitro-5,5'-dithio-dibenzoic acid.

In the title compound, C(14)H(8)N(2)O(8)S(2), the asymmetric unit contains two independent 2,2'-dinitro-5,5'-dithio-dibenzoic acid (Dina) mol-ecules with roughly the same conformation. In the crystal structure, strong inter-molecular O-H⋯O hydrogen bonds link the organic mol-ecules into a one-dimensional zigzag chain along the a axis. The dihedral angles between the two aromatic rings [109.3 (2) and 103.1 (3)°] are larger than that (88.95°) observed in a structure of the compound with a solvent water mol-ecule [Shefter & Kalman (1969), J. Chem. Soc. D, p. 1027]. Such a difference may be explained by the occurrence of O-H⋯O hydrogen bonds involving the water mol-ecule in the previously reported structure.