(E)-2,4-Dihydroxy-benzaldehyde 4-ethyl-thio-semicarbazone-4,4'-bipyridine-water (4/7/2).

The asymmetric unit of the title compound, 7C(10)H(8)N(2)·4C(10)H(13)N(3)O(2)S·2H(2)O, contains two independent 2,4-hydroxy-benzaldehyde 4-ethyl-thio-semicarbazone mol-ecules, three and a half 4,4'-bipyridine mol-ecules and one water mol-ecule. Two of the 4,4'-bipyridine mol-ecules lie on general positions and the other three on centers of inversion. The two 4,4'-bipyridine mol-ecules on general positions and one of the three on special positions are disordered over two positions each with an occupancy of 0.50. The -NH-C(=S)-NH-NC fragment is close to planar in the two 2,4-hydroxy-benzaldehyde 4-ethyl-thio-semicarbazone mol-ecules (r.m.s. deviations = 0.04 and 0.05 Å). In the crystal, the Schiff base, N-heterocycle and water mol-ecules engage in O-H⋯O, O-H⋯N and N-H⋯O hydrogen-bonding inter-actions, generating a layer structure.