15] Dielectric dispersion measurement of dielectric constant and conductivity

Abstract

Publisher Summary This chapter discusses the presentation of the basic principles involved and of methods used to obtain the necessary parameters. Although the purpose of this chapter is to describe the experimental techniques of dielectric measurements, a brief description of basic theories seems desirable. In particular, the development of microwave techniques now helps to extend the frequency to the millimeter wavelength region, and the dielectric relaxation of many molecules can be established. However, the measuring techniques have been improving rapidly, and experimental data are much more accurate and reliable. Because the dielectric measurements with protein or enzyme solutions are usually undertaken at radio frequencies—that is, between 100 KHz and 100 MHz—the discussion of techniques is limited to this frequency region. The techniques at higher frequencies are entirely different and use must be made of transmission-line and waveguide systems. However, the dielectric constant measurement of aqueous polar solutions is certainly much more difficult than that of organic compounds whose conductivities are low. There have been numerous measurements of dielectric constant on small polar molecules in nonaqueous solvents.