Electrode potential, effect current oscillation

Table 4.12. Effect of polarization current and material types of the prism and support on oscillation time r of the pendulum (min) and electrode potential shift of the support At/ (mV)...

As the potential that is applied across the electrodes is increased, the ionic velocities increase. Thus, the detector signal is proportional to the applied potential. This potential can be held to a constant value or it can oscillate to a sinusoidal or pulsed (square) wave. Cell current is easily measured however, the cell conductance (or reciprocal resistance) is determined by knowing the potential to which the ions are reacting. This is not a trivial task. Ionic behavior can cause the effective potential that is applied to a cell to decrease as the potential is applied. Besides electrolytic resistance that is to be measured, Faradaic electrolysis impedance may occur at the cell electrodes resulting in a double layer capacitance. Formation of the double layer capacitance lowers the effective potential applied to the bulk electrolyte. 

Electrodes coated with Pd-(Ni-Zn)/C and Pd-(Ni-Zn-P)/C are apparently stable for the oxidation of ethanol as shown by the chronopotentiometry experiments illustrated in Fig. 21. hi fact, there is some potential oscillation in the first two-three honrs of ethanol oxidation at a constant current density of 3.0 mA cm, then no oscillation at all, as well as a potential increase by only a few tens of mV after 5.5 h. Both features suggest the absence of effective catalyst deterioration, for example by the formation of strongly adsotbed species on the catalysts surface. 

To assess the effect of drugs on a neuromuscular synapse, either the endplate potentials or the intensity of muscular contractions in response to rhythmic electric stimulation of the nerve are registered In the first case, the evoked gradual responses of the neuromuscular junctions are recorded by means of thin electrodes. Changes in the magnitude of these responses are criteria of the efficiency of the drugs with respect to naptic transmission. In the second case, the facilitation or inhibition of synaptic transmission is reflected by either an increase or a decrease in the intensity of muscular contractions. For convenience, the latter are usually transformed into corresponding oscillations of electric current. 

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