The asymmetric unit of the title compound, C3H5N2 +·C6H2N3O7 −·C3H4N2·H2O or H(C3H4N2)2 +·C6H2N3O7 −·H2O, contains a diimidazolium cationic unit, one picrate anion and one mol­ecule of water. In the crystal, the components are connected by N—H⋯O, N—H⋯N and O—H⋯O hydrogen bonds, forming a two-dimensional network parallel to (001). In addition, weak inter­molecular C—H⋯O hydrogen bonds lead to the formation of a three-dimensional network featuring R 5 5(19) rings.

The asymmetric unit of the title compound, C8H8O2, contains two crystallographically independent mol­ecules, which form dimers linked by O⋯H—O hydrogen bonds. The benzene rings in the dimers are inclined at a dihedral angle of 7.30 (8)° and both methyl groups display rotational disorder. This redetermination results in a crystal structure with significantly higher precision than the original determination [Ellas & García-Blanco (1963 ▶). Acta Cryst. 16, 434], in which the authors reported only the unit-cell parameters and space group, without any detailed information on the atomic arrangement. In the crystal, dimers are connected by weak C—H⋯O inter­actions, forming R 2 2(10) and R 4 4(18) rings along [110] and an infinite zigzag chain of dimers along the [001] direction also occurs.