The dispersion of the dielectric constant of some dilute solutions of polar compounds in non-polar solvents

A method of measuring at microwave frequencies both the real (ε') and imaginary (ε″) part of the complex dielectric constant of liquids with a loss tangent less than 0,05 is described. The method uses a vertical section of rectangular waveguide for both propagation and for the liquid cell, which is sealed from the rest of the waveguide by a thin mica window. The waveguide cell is terminated by a micrometer driven open circuit plunger. A klystron, square wave modulated at 1000 cps, is used to generate the signal, while a slotted section of waveguide, directly below the cell, with a probe coupled to a silicon crystal is the detection device. The probe is micrometer driven. The signal power level at the probe is indicated by the output of an audio amplifier fed by the crystal and tuned to the modulation frequency.