title: 4,4'-[(5-Carb-oxy-1,3-phenyl-ene)bis-(-oxy)]dibenzoic acid.
abstract: In the title compound, C(21)H(14)O(8), the central benzene ring makes dihedral angles of 77.8 (6) and 75.9 (5)° with the outer benzene rings. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds involving carboxyl groups, forming one-dimensional ladders. Two-dimensional layers are formed by inter-penetration of these one-dimensional ladders.
authors.forename: Chao
authors.initials: C
authors.lastname: Du
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Ge
authors.initials: G
authors.lastname: Tian