Dielectric spectroscopy of aqueous solution of fulvic acids

9 pages, 2 figures, 3 tables, 39 references.-- Publicado en el capítulo: Session 1: Isolation, Fractionation, and Characterization.-- Humic Substances in the Aquatic and Terrestrial Environment, Proceedings of an International Symposium, celebrado del 21-23, agosto, 1989 en Linköping, Suecia.-- Este volumen 33, referido en la Citación, consta de 514 páginas, 150 figuras y 57 tablas.The complex dielectric spectrum of aqueous solutions (10% w/w) of fulvic and polymaleic acids has been measured at various frequencies between 1 MHz and 40 GHz. Similar to pure water a dispersion/dielectric loss region emerges in the range above 1 GHz. The measured spectra have been analytically represented by the empirical Cole-Cole relaxation spectral function to yield values for the extrapolated high- and low-frequency permittivity, the principal dielectric relaxation time, the relaxation time distribution parameter and the specific electric d.c. conductivity. In correspondence with aqueous solutions of synthetic organic molecules, the low-frequency permittivity of the fulvic acid/water mixtures is reduced, and the principal dielectric relaxation time is enhanced with respect to the pure water value. As with solutions of polyacrylic acid no solute contributions to the real part of the dielectric spectrum are found.Peer reviewe

A Comparison of Dielectric Measurement Methods for Liquids in the Frequency Range 1 GHz to 4 THz

From measurements on hyperpure and commercially pure low- to high-loss liquids over a wide spectral range and using a variety of experimental equipment, we have been able for the first time to quantify both the systematic and the random uncertainties to which extra-high-frequency dielectric measurements are subject. From our measurements it has become possible to specify certain liquids and solids as standard reference materials for the calibration of high-frequency dielectric measuring equipment. Copyright © 1980 by The Institute of Electrical and Electronics Engineers, Inc.SCOPUS: ar.jinfo:eu-repo/semantics/publishe