Comparison of Iron and Aluminum Hydroxy Interlayers in Montmorillonite and Vermiculite: I. Formation

Hydroxy‐Al and ‐Fe interlayers were formed in montmorillonite and vermiculite by adding AlCl 3 or FeCl 3 and NaOH in amounts to give a wide range of pH. The resulting chloritic intergrades were examined aften 10 days, 6 months, and 1 year. Aluminum‐interlayered montmorillonite formed at pH 4.6 after 10 days showed the essential X‐ray characteristics of chlorite. The best iron interlayers in montmorillonite prevented collapse upon K‐saturation and heating but did not prevent expansion upon solvation. Aluminum‐interlayered vermiculite showed partial collapse on K‐saturation and heating. Acid conditions favored interlayer formation with aluminum and iron in montmorillonite and with aluminum in vermiculite. Iron interlayers in vermiculite were favored by alkaline conditions. Iron interlayers decreased with time. Aluminum interlayers formed in montmorillonite with acid conditions decreased sharply with time. Aluminum interlayers in vermiculite and those formed under alkaline conditions in montmorillonite, showed some tendency to increase with time.