4,4'-Bipyridine-4-(p-toluene-sulfonamido)-benzoic acid (1/2).

In the title compound, C(14)H(13)NO(4)S·0.5C(10)H(8)N(2), the two benzene rings are nearly perpendicular to each other [dihedral angle = 83.21†(10)°]. The bipyridine mol-ecule is centrosymmetric, the mid-point of the C-C bond linking the pyridine rings being located on an inversion center. Inter-molecular N-H⋯O and O-H⋯N hydrogen bonds and weak inter-molecular C-H⋯O hydrogen bonds are present in the crystal structure.