The Chemistry of the Surfaces of the Acid Forms of Natural Layer Silicates

Modern ideas about the nature of the exchangeable acidity of a group of layer silicates (clay minerals) are described and the results obtained during the last decade with the aid of physical and physicochemical techniques are surveyed. The dependence of the surface acidity on non-stoichiometric substitutions in the structure of the minerals, the influence of a number of factors on the spontaneous conversion of the H-forms of the silicates into Al-Fe-Mg-forms, the mechanism of this phenomenon, the ion-exchange properties and the thermal stabilities of the H- and Al-Fe-Mg-forms, and other problems are examined. The bibliography includes 80 references.