Packing diagram of (IV) with the outline of the unit cell. View is onto the (010) plane. The layers of 4-sulfobenzoic acid anions are in the center of the cell with the silver and potassium ions (disordered over the same site) situated in between the layers. O—H⋯O hydrogen bonds between the carboxylic groups and coordinated water molecules are shown as dashed bonds. H atoms bonded to C atoms have been omitted. Displacement ellipsoids are drawn at the 70% probability level.