Method for Obtaining Streaming Orientation and Simultaneous Determination of Dielectric Properties in Macromolecular Solutions

Abstract

A method has been devised for the measurement of the dielectric constant and the specific conductance of aqueous solutions undergoing streaming with velocity gradients between 0 and 10 000 sec⁻¹. The solution to be investigated is placed in the annular space between two concentric cylinders forming the measuring cell. Electrodes are inserted in the walls of the cylinders of which the outer is fixed and the inner is rotated. Two types of cells are used; the electrical field in one case being perpendicular to and in the other case parallel with the stream lines. The impedance of the cell with the solution investigated is determined with a specially constructed Schering bridge making measurements possible in the frequency range 0.05 to 5 megacycles per second and at specific conductances of 1 to 200 μmho per centimeter. The advantage of the bridge circuit employed is that the conductance of the cell is balanced by a variable air condenser, making possible an accuracy of 0.1 percent in the values for both conductance and dielectric constant. Excellent mechanical and electrical stability and a low interference level are necessary for high accuracy. Experiments with solutions of sodium thymonucleate show that the current interpretation of the dielectric properties of macromolecules must be revised. The term streaming dielectric investigations is suggested as a suitable name for studies with the type of instrument described.