5-Amino-6-methyl-quinolin-1-ium hydrogen malonate-malonic acid (2/1).

The asymmetric unit of the title compound, 2C10H11N2(+)·2C3H3O4(-)·C3H4O4, consists of one 5-amino-6-methyl-quinolin-1-ium cation, one hydrogen malonate (2-carb-oxy-acetate) anion and one-half mol-ecule of malonic acid which lies on a twofold rotation axis. The quinoline ring system is essentially planar, with a maximum deviation of 0.062 (2) Å for all non-H atoms. In the anion, an intra-molecular O-H⋯O hydrogen bond generates an S(6) ring. In the crystal, the components are linked via N-H⋯O and O-H⋯O hydrogen bonds into layers parallel to the ac plane. The crystal structure also features weak C-H⋯O hydrogen bonds and a π-π stacking inter-action with a centroid-centroid distance of 3.8189 (10) Å.