Ethane-1,2-diaminium bis-(4-carb-oxy-2-propyl-1H-imidazole-5-carb-oxy-ate) monohydrate.

In the title hydrated molecular salt, C(2)H(10)N(2) (2+)·2C(8)H(9)N(2)O(4) (-)·H(2)O, an intra-molecular O-H⋯O hydrogen bond occurs in the anion, forming an S(7) ring. The -CO(2) and -CO(2)H groups make dihedral angles of 3.2 (2) and 2.0 (3)°, respectively, with the five-membered ring. In the crystal, N-H⋯O, N-H⋯N and O-H⋯O hydrogen bonds lead to the formation of a three-dimensional supra-molecular architecture. The methyl group in the anion is disordered over two sets of sites in a 0.716 (9):0.284 (9) ratio. The ethylenediamine cation is generated by symmetry and the water molecule lies on a twofold axis.