The title compound, C(16)H(12)N(2)O(6)·2C(3)H(7)NO, lies across a crystallographic inversion centre which is situated at the midpoint of the central N-N bond. The substitution at the C=N bond adopts a trans configuration and it is essentially coplanar with the benzene ring [N-C-C-C torsion angles = -173.9 (4) and 6.4 (6)°]. All torsion angles involving non-H atoms are close to 180°. Intra-molecular O-H⋯O and weak C-H⋯O hydrogen bonds form S(6) and S(5) ring motifs, respectively, while inter-molecular O-H⋯O and weak C-H⋯O hydrogen bonds connect the Schiff base mol-ecule to solvent dimethyl-formamide mol-ecules.