Biphenyl-3,3',4,4'-tetra-carboxylic acid dihydrate.

The asymmetric unit of the title compound, C16H10O8·2H2O, contains one-half of the centrosymmetric organic mol­ecule and one water mol­ecule. The dihedral angles between the carboxyl­ate groups and the adjacent phenyl ring are 71.31 (3) and 16.67 (3)°, while the carboxyl­ate groups are oriented at a dihedral angle of 72.01 (3)°. In the crystal structure, inter­molecular O—H⋯O and bifurcated O—H⋯(O,O) hydrogen bonds link the mol­ecules to form a three-dimensional supra­molecular network.