Complexes formed by macroscopic vermiculite crystals and n-alkylammonium ions with alkyl chains of 3‐4 carbon atoms swell unidimensionally in water until the silicate layers are several hundred Ångströms apart.

The initiation of swelling is thought to involve the development of “icebergs” of the Frank-Evans type around the alkylammonium ions. Hydration of the oxygen surfaces of the silicate layers may also be a significant factor in the swelling process.

Cataphoresis experiments on finely dispersed aqueous suspensions indicate the presence of diffuse double layers of positive ions around negatively charged silicate particles. Further swelling on applying an electric field to individual swollen crystals immersed in water and dilute solutions also has been observed.

The viscosimetric constants of aqueous suspensions of certain homoionic forms of mont-morillonite and attapulgite were measured following adsorption of different kinds and quantities of organic polymers. Dissymmetry and interaction of the clay—organic complexes were then calculated from the Schulz-Blaschke equation and their structures deduced.

A positive, linear relationship was found between the dissymmetry of H- and Al-montmorillonite, respectively, and the amount of vinyl acetate maleic anhydride (VAMA) adsorbed-H-montmorillonite displayed the greater dissymmetry and it is inferred that H-montmoril. lonite complexes consist of an edge-to-edge linkage of clay particles through lattice-aluminumcarboxyl bonds. Al-montmorillonite permits three kinds of linkage: edge-to-edge (as with H-montmorillonite), external flat surface-to-surface (producing a “stacked” structure), and surface-to-edge, the last two involving exchangeable aluminum-carboxyl bonds. Edge-to-edge linkages probably predominate.

Ca-montmorillonite is unaffected by less than 8 parts of VAMA per thousand of clay. Edge-to-edge linked clay particles appear at this ratio and interaction diminishes. Delayed structural organization can be explained by low polymer adsorption at high initial pH. Maximum dissymmetry of H-montmorillonite-VAMA complexes occurred after titration with NaOH to pH between 6 and 8, above which mutual repulsion between highly dissociated polymer and clay may restrict linkage.

H-attapulgite—VAMA complexes are dissymmetrical for low VAMA adsorption but increased adsorption reduces dissymmetry and bundles of edge-to-edge linked particles are formed.

Probable structures of montmorillonite complexes with other polymers are also discussed.

The amount of moisture in a soil and its orientation to individual soil particles may be influenced by small additions of organic cationic compounds. Clay particles adsorb these cations, and because of their hydrophobic nature a waterproofing effect occurs. Thermodynamic considerations are presented to explain the strength retention of treated soils.

The smectic clays from Cabo de Gata region, Almeria, Spain, are composed mainly of montmorillonite, but they contain appreciable quantities of fibrous clay minerals, some of which are of the palygorskite type. However, there also is a mineral that has properties intermediate between those of palygorskite and sepiolite. Its structure seems to be a random intergrowth of both.