Bis(2-amino-4-methyl-pyridinium) terephthalate tetra-hydrate

In the crystal structure of the title salt, 2C(6)H(9)N(2) (+)·C(8)H(4)O(4) (2-)·4H(2)O, the terephthalate carboxyl-ate groups inter-acts with the 2-amino-4-methyl-pyridinium cations via a pair of N-H⋯O hydrogen bonds, forming an R(2) (2)(8) ring motif. The water mol-ecules form an R(6) (6)(12) ring motif through O-H⋯O hydrogen bonds and these motifs are fused, forming a supra-molecular chain along the c axis. The R(2) (2)(8) and R(6) (6)(12) ring motifs are connected via O-H⋯O hydrogen bonds. In addition, π-π stacking inter-actions are observed between the pyridinium rings [centroid-centroid distance = 3.522 (12) Å].