British Association Discussions: Physical Chemistry of Clay

Abstract

IT is a remarkable tribute to the liberal outlook of Section B (Chemistry) of the British Association that the four principal contributors to the discussion on clays held on August 22 at Cambridge were physicists. The basic principles governing the chemistry of the silicates are, as Prof. W. L. Bragg explained, clearly revealed in their crystal structure. Every silicon atom is surrounded by four oxygen atoms in tetrahedral arrangement. In olivine the (SiO⁴)""groups are separate, while in silica and the feldspars each oxygen is a component of two tetrahedra. Between these extremes we find the pyroxenes and amphiboles, in which the tetrahedra are linked by common oxygens into parallel chains, and minerals, like mica, in which the tetrahedra are linked into parallel sheets.