2,4-Diamino-6-methyl-1,3,5-triazin-1-ium hydrogen oxalate.

The title compound, C(4)H(8)N(5) (+)·C(2)HO(4) (-), was obtained from the reaction of oxalic acid and 2,4-diamino-6-methyl-1,3,5-triazine. The protonated triazine ring is essentially planar with a maximum deviation of 0.035 (1) Å, but the hydrogen oxalate anion is less planar, with a maximum deviation of 0.131 (1) Å for both carbonyl O atoms. In the crystal, the ions are linked by inter-molecular N-H⋯O, N-H⋯N, O-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional network. Weak π-π [centroid-centroid distance = 3.763 Å] and C-O⋯π inter-actions [O⋯centroid = 3.5300 (16) Å, C-O⋯centroid = 132.19 (10)°] are also present.