Bis(4,4'-methyl-enedianilinium) naphthalene-1,5-disulfonate dihydrate.

The asymmetric unit of the title salt, C(13)H(16)N(2) (2+)·C(10)H(6)O(6)S(2) (2-)·2H(2)O, consists of one dication located on a general position, half each of two centrosymmetric dianions, and two uncoordinated water mol-ecules in general positions. In the dication, the dihedral angle between the benzene rings is 74.67 (6)°. The cations and anions inter-act through N-H⋯O hydrogen bonds. The NH(3) (+) functional groups are also involved in N-H⋯O hydrogen bonds with the water mol-ecules, forming an infinite three-dimensional framework in the crystal structure.