Structural Model for Benzidine-Vermiculite

P. G. Slade and M. Raupach
CSIRO Division of Soils, Glen Osmond, South Australia 5064, Australia

Abstract: A combination of X-ray diffraction, infrared, and chemical data has established that the ion exchange of vermiculite with singly charged benzidine cations in an aqueous solution at pH 1.6 results in a black, highly ordered benzidine-vermiculite intercalate. The intercalate has a basal spacing of 19.25 Å and a primitive unit cell with “a” and “b” edges parallel and equal to those of vermiculite. The number of benzidine molecules per cell is equal to its electric charge. In this structure the benzidine molecules are steeply inclined to the silicate surfaces and close-packed within domains. The domains contain alternating rows of benzidine cations; from row to row the planes are either approximately parallel or perpendicular to the (120) plane, but along any one row the planes of the aromatic rings are parallel to each other. Hydrogen bonding operates between amine nitrogens and surface oxygens.

Key Words: Benzidine • Hydrogen bonding • Intercalation • Vermiculite • X-ray diffraction

Clays and Clay Minerals; August 1982 v. 30; no. 4; p. 297-305; DOI: 10.1346/CCMN.1982.0300408
© 1982, The Clay Minerals Society
Clay Minerals Society (www.clays.org)