2-Amino-5-chloro-pyridin-1-ium barbiturate dihydrate.

In the title hydrated salt, C5H6ClN2 +·C4H3N2O3 -·2H2O, the asymmetric unit contains two cations, two anions and four water mol-ecules of crystallization. In the extended structure, the barbiturate (2,4,6-trioxo-1,3-diazinan-5-ide) anions form a wave-like supra-molecular [001] chain decorated by the cations, mediated by numerous N-H⋯O hydrogen bonds. Adjacent chains are cross-linked by [010] chains of water mol-ecules featuring four- and six-membered rings and five-membered carboxyl-ate aggregates via O-H⋯O hydrogen bonds.