Conductance, electrolytic high-frequency

At these high frequencies, the retarding effect of the ion-atmosphere on the movement of a central ion is greatly decreased and conductance tends to be increased. The capacitance effect is related to the absorption of energy due to induced polarisation and the continuous re-alignment of electrically unsymmetrical molecules in the oscillating field. With electrolyte solutions of low dielectric constant, it is the conductance which is mainly affected, whilst in solutions of low conductance and high dielectric constant, the effect is mostly in relation to capacitance. 

Electrolytes, like electronic conductors, obey Ohm s Law, except under such extreme conditions as those involving very high voltages and/or very high-frequency alternating currents. The conductance of an electrolyte is calculated from measurements of its resistance. 

Debye-Falkenhagen effect physchem The increase in the conductance of an electrolytic solution when the applied voltage has a very high frequency. d3 bT fal-kon,hag-on i,fekt ... 

DEBYE-FALKENHAGEN EFFECT. The variation of the conductance of an electrolytic solution with frequency. This effect, which is noted at high frequencies, is also called the dispersion of conductance,... 

Cells for Conductimetry. Reliable and precise measurements of electrolytic conductance require attention to the design of cells, electrodes, and measuring circuitry. Extraction of an ohmic resistance from AC bridge measurements is not a trivial task, particularly in solutions with high resistance (such as organic solvents) or low resistance (molten salts). Expositions of the principles are provided in monographs that emphasize aqueous solution,54,55 and in a review of conductimetry and high-frequency oscillometry that emphasizes analytical applications.56... 

Membrane capacitance and conductance were measured using the Wayne-Kerr admittance bridge and measurements were made between 100 Hz and 20 KHz using a PAR lock-in amplifier model 124. One of the results obtained is shown in Figure 1. The dotted curve shown in this figure indicates measured values at high frequencies and the downward slope arises from the presence of electrolyte solutions between the membrane and electrodes. 

A high electrolyte conductivity is essential. It is correctly measured by impedance spectroscopy at high frequency. 

Debye-Falkenhagen effect - Debye and - Falken-hagen predicted, that in - electrolyte solutions the ionic cloud may not be established properly and maintained effectively when the ion and the cloud are exposed to an alternating (AC) electric field in particular of high frequency. Thus the impeding effect of the ion cloud on the ion movement should be diminished somewhat resulting in an increased value of the ionic conductance. Above frequencies of v 107 to 108 s-1 this increase has been observed, see also - Debye relaxation time. 

When R2 R, the polymer is more conducting than the pores. The Randles circuit, which is located at the polymer/electrolyte interface (case b), shunts the resistive ionic rail through the polymer. At high frequencies, the equation can be simplified to... 

Conductance Determinations at High Voltage and High Frequency.— The electrolytic conductances of solutions with alternating current of very high frequency or of high voltage have acquired special interest in connection with modern theories of electrolytic solutions. Under these... 

It may be pointed out in conclusion that the conductance phenomena with very high frequency currents and at high potential gradients provide striking evidence for the theory of electrolytic conductance, based on the existence of an ionic atmosphere surrounding every ion, proposed by Debye and Huckel and described in this chapter. Not only does the theory account qualitatively for conductance results of all types, but it is also able to predict them quantitatively provided the solutions are not too concentrated. 

Wang et al. (1992) developed a new technique for the measurement of electrical conductivity of fiuoride melts, which employs the principle of a Continuously Varying Cell Constant (CVCC) through a moving platinum disc electrode in a relatively large diameter capillary tube-type conductivity cell. At the same time, the real component of the circuit impedance, R a, at a fixed high-frequency current is measured. Since the Rm versus the cell constant plot is linear, the electrical conductivity of the electrolyte is given by the relation... 

To avoid artifacts in impedance measurements when modulating the input voltage of the potentiostat at high frequencies (>10 kHz), the reference electrode should be short-circuited via a capacitance of 10 nF and a Pt wire dipped into the solution in the main part of the cell (Fig. 4.2). The surface of the counter electrode should be sufficiently large so that its interface with the electrolyte does not influence the current-potential curve. Usually a platinized Pt sheet is used as a counter electrode. The electrolyte is made conductive by adding an inert salt of a concentration in the range of 10-3-10- M. 

Electrolytic Conductances at High Potentials and High Frequencies All the conclusions concerning the conductances of solutions of electrolytes outlined in this and the preceding chapters have been based on measurements of conductances made using alternating current... 

Kohlrausch established that electrolytic solutions obeyed Ohm s law accurately once the effect of the electrolysis products was eliminated by using high-frequency alternating current. Kjohlrausch also showed from the experimental data that the conductivity of a solution couId "Be mposed of separate contributions from each ion this is known as Kohlrausch s law of the independent migration of ions. 

Ohm s law applies to both metallic conductors and electrolyte solutions. However, anomalies occur under special conditions such as high voltages or very high frequencies. Our emphasis will be to explore electrolytic conductance for analytical uses under the more ideal conditions of low volta (1 to 100 V) and low frequencies (0 to 5000 Hz). We will also introduce the technique of oscillometry, which is an... 

The frequency dispersion of porous electrodes can be described based on the finding that a transmission line equivalent circuit can simulate the frequency response in a pore. The assumptions of de Levi s model (transmission line model) include cylindrical pore shape, equal radius and length for all pores, electrolyte conductivity, and interfacial impedance, which are not the function of the location in a pore, and no curvature of the equipotential surface in a pore is considered to exist. The latter assumption is not applicable to a rough surface with shallow pores. It has been shown that the impedance of a porous electrode in the absence of faradaic reactions follows the linear line with the phase angle of 45° at high frequency and then... 

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