X-Ray Study of the Interlayer Region of a Barium-Vermiculite

An X-ray diffraction analysis of a barium-vermiculite shows it to have a triclinic unit cell with the following dimensions a = 5.33, b = 9.26, c = 12.47 Å, α = 100.75°, ß = 93.5° and γ = 90°. The proposed structure, adjusted in space group Cl, has the exchangeable cations approximately over the ditrigonal holes of the silicate surface and on either side of a hexagonal network of water molecules extending over the middle of the interlamellar region. The interlayer material imposes a relative displacement of ± b /4 on adjacent silicate sheets. The importance of these displacements, not previously found in layer silicates, is emphasized.