Bentonite Solution Research Articles

Streaming Birefringence as a Hydrodynamic Research Tool—Applied to a Rotating Cylinder Apparatus above the Transition Velocity

Streaming birefringence was studied in the annular space between a fixed outer and a rotating inner cylinder at velocities on both sides of transition to Taylor vortex flow. With a well-collimated light beam, quantitative measurements were possible as close as 0.1 mm from a wall. For an aqueous colloidal solution of bentonite, shear stress could be evaluated from birefringence measurements only when, for a given birefringence, the angle of extinction was the same in the unknown flow as in a known laminar flow. In turbulent shear flow this is not generally the case. For a pure liquid, ethyl cinnamate, the angle of extinction remained at 45° to the streamlines, within experimental error, under all flow conditions obtainable; thus even in turbulent shear flow the birefringence appears to arise primarily from the principal stresses. Assuming birefringence proportional to mean shear stress permits construction of a velocity profile across the gap, yielding the correct value of velocity of the moving wall within limits of experimental error. Thus in this type of two-dimensional shear flow the mean shear stress can be measured by means of the streaming birefringence of a pure liquid.

Theory of Anisotropic Colloidal Solutions

The appearance of anisotropic phase in the unipolar coacervations of tobacco mosaic virus or bentonite solutions are explained theoretically, and the recent theory of Onsager is confirmed. As has been emphasized already by Langmuir, the repulsive forces between solute molecules and the force arising from thermal agitation are decisive for the occurrence of the anisotropic phase. The critical concentrations where the anisotropic phase starts are explicitly determined for prolate and oblate spheroidal and also cylindrical solute molecules. It is found that the critical concentrations are all inversely proportional to the axial ratios, and therefore, it is explained why these critical concentrations are of the same order of magnitude in spite of the totally different characters of solute molecules

Preliminary Report of the Use of Sulfadiazine Bentonite Solution in the Treatment of External Otitis

Preliminary Report of the Use of Sulfadiazine Bentonite Solution in the Treatment of External Otitis

Electro-Optical Field Mapping

As a result of the discovery of an unusually large electro-optical effect in certain colloidal solutions of bentonite it has become possible to study and measure inhomogeneous electric fields by an optical method which is analogous to that of photoelasticity. Observations with crossed Polaroids show two orthogonal systems of lines. The isoclinic lines determine the field direction, the isochromatic lines give the field intensity in any point, of a plane field. The method employs a.c. potentials of less than 200 volts.