Libratory modes of water molecules in tutton salts

The existence of rocking, wagging and twisting librations of different types of water molecules in tutton salts has been established from their ir spectra. These bands have been identified, following the intensity criterion of Miyazawa. The present assignments indicate that the bands due to libratory motion of H₂O III in NH₄Mn-, KNi-, KCo and KMn- and of H₂O I in KMn- and KCu- tutton salts are out-of-plane H-bonded. The strength of the hydrogen bonding is the weakest in the (NH₄)₂Fe(SO₄)₂.6H₂O.