Bis(8-hy-droxy-quinolinium) naphthalene-1,5-di-sulfonate tetra-hydrate.

The inter-action between 8-hy-droxy-quinoline (8HQ, C 9 H 7 NO) and naphthalene-1,5-di-sulfonic acid (H 2 NDS, C 10 H 8 O 6 S 2 ) in aqueous media results in the formation of the salt hydrate bis-(8-hy-droxy-quinolinium) naphthalene-1,5-di-sulfonate tetra-hydrate, 2C 9 H 8 NO + ·C 10 H 6 O 6 S 2 2- ·4H 2 O. The asymmetric unit comprises one protonated 8HQ + cation, half of an NDS 2- dianion symmetrically disposed around a center of inversion, and two water mol-ecules. Within the crystal structure, these components are organized into chains along the [010] and [10] directions through O-H⋯O and N-H⋯O hydrogen-bonding inter-actions, forming a di-periodic network parallel to (101). Additional stabilizing inter-actions such as C-H⋯O, C-H⋯π, and π-π inter-actions extend this arrangement into a tri-periodic network structure.