Abstract: 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.