N,N′-Di­hydroxy­benzene-1,2:4,5-tetra­carboximide dihydrate

In the title compound, C(10)H(4)N(2)O(6)·2H(2)O, the organic mol­ecule has crystallographically imposed inversion symmetry. The atoms of the three fused rings of the mol­ecule are coplanar within 0.0246 (8) Å, while the two hy­droxy O atoms are displaced from the mean plane of the mol­ecule by 0.127 (1) Å. In the crystal, infinite near-planar layers of close-packed mol­ecules are formed by hydrogen bonding between water O—H donor groups and carbonyl O-atom acceptors, and by weak inter­actions between C—H donor groups and water O-atom acceptors. The layers are parallel to the {102} family of planes. The stacked planes are held together by hydrogen bonding between N—OH donor groups and water O-atom acceptors.