Packing diagram of (III) with the outline of the unit cell. View is onto the (001) plane. The layers of 4-sulfobenzoic acid anions are evident with the silver and potassium ions situated in between the layers. O—H⋯O hydrogen bonds connecting the carboxylic H atoms and carboxylate O atoms of adjacent layers are shown as dashed bonds. H atoms bonded to C atoms have been omitted. Displacement ellipsoids are drawn at the 70% probability level.