Light-scattering studies on suspensions of orientated attapulgite

Abstract

A study is reported of the light scattered by aqueous suspensions of the clay mineral attapulgite when the dispersions were subjected to alternating electric fields. Prior to the application of these fields, conventional measurements indicated that the dispersed particles were of weight average molecular weight 5·9×109 and of 1·1 μm in length. Electron micrographs confirmed the approximate cylindrical form of the particles. The theory for the change in the intensity and shape of the angular scattering diagram when alternating electric fields are applied to the suspensions and the requirements of a suitable apparatus to detect these changes are briefly outlined. The observed intensity changes for fields of magnitude up to 170 v cm−1 and frequencies below 150 Hz indicated that the attapulgite particles were characterized by an effective permanent dipole moment of magnitude 4·2×10−6 e.s.u. across the particles and an electrical anisotropy of 2·4×10−13 e.s.u. along the rods. The magnitude of the latter indicates that a surface rather than a bulk conductivity is involved and that attapulgite is probably synonymous with palygorskite. The frequency dependence of the intensity changes enabled a value of the rotary diffusion constant of 60 s−1 to be determined. The study is closed with a brief comparison between the electric field light scattering as used in these experiments and the similar but better-known Kerr electro-optical effect.

A free Lie algebra as a module over the full linear group

“…Light scattering measurements were made on a modified (Jennings andPlummer 1968, Jennings 1969) Sofica photometer.? An improved design of the parallel, horizontal electrode assembly was used, which corresponded to the condition R = 90 ' .…”