Abstract
An evaluation of the factors affecting interlayer expansion of the mica type layered minerals was made by X‐raying various dehydrated forms of montmorillonite and vermiculite while immersed in liquids of varying dipole moments and dielectric constants. The results showed that the extent of interlayer expansion was determined by the size, charge, and total amount of the interlayer cations and by the magnitude of the dipole moment and the dielectric constant of the immersion liquid. The results were explained on the basis of the nature of the electrostatic interlayer attractive forces within the crystal lattice itself and by the laws governing complex formation between charged particles.