l-Histidinium dipicrate dihydrate.

In the title mol-ecular salt, C6H11N3O2 (2+)·2C6H2N3O7 (-)·2H2O, the histidine mol-ecule exists as a histidinium dication, being protonated at the N atom of the imidazole ring. The charges are balanced by two picrate anions and the compound crystallizes as a dihydrate. In the crystal, the components are linked via N-H⋯O and O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions, forming a three-dimensional supermolecular structure.