Nitrobenzene and benzoic acid are coordinated through water molecules to the more highly polarizing exchangeable cations in the Inte rlayer space of montmorillonite, but are directly coordinated to NH/ and possibly also K+: On dehydration of the adsorptlon complexes the nitrobenzene and benzoic acid become directly coordinated to all of the exchangeable cations investigated. Benzoate ion was also formed in amounts which were dependent on the exchangeable cations.