Viscoelectric effect

The potential decay d /(x)/dx (equal to the electric field) across the double layer may further influence the viscosity of the liquid. This is known as the viscoelectric effect. In electrical double layers, the electric field may be sufficiently strong to 

In order to account for the viscoelectric effect, the expressions relating the measured quantity to should be modified by writing ti of the liquid as a function of the electric field. 

For a series of (organic) liquids it has been shown that the viscosity is increased by applying an electric field according to the empirical relationship 

The subscripts indicate the presence (Z ) or absence (0) of an electric field. The factor/is the viscoelectric constant for a variety of liquids,/has a value of about 2 X 10 V m. It means that the viscosity of the liquid undergoes a 2%-300% increase by applying an electric field of 10 -10 V m . In electrical double layers such field strengths are quite realistic. For the diffuse part of the electrical double layer, d /(x)/djc can be calculated using Equation 9.27 or 9.28. For instance, in a solution of a 1 1 electrolyte of 0.1 M ionic strength, the field strength at x where / = 50mV amounts to 6.4 x 10 V m .  

By way of example, the influence of the viscoelectric effect on the relation between electrophoretic mobility and (for ka 1, i.e., when the electrophoretic retardation is negligibly small) is elaborated as follows. Based on Equation 10.5, with Q = 0, the relation between v f and is given by 

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Electrokinetic phenomena such as electroosmosis, streaming potential, and viscoelectric effects (Chapter 12)... 

How do charges on particles change the viscosity of a dispersion What are electroviscous effects How do they differ from the viscoelectric effect ... 

Hunter, R. J., Zeta Potentials in Colloid Science Principles and Applications, Academic Press, London, 1981. (Advanced. A research-level monograph on electrokinetic phenomena and electroviscous and viscoelectric effects.)... 

An expression such as Equation (11.56) may be used to estimate E (= chp/dx) in the double layer. Table 12.1 shows values of E evaluated by means of this equation for a variety of xl/0 values and 1 1 electrolyte concentrations. It will be noted that for high values of /0 and high ionic strengths, the field in the double layer may be large enough to produce a very significant viscoelectric effect. 

What is the viscoelectric effect How does it affect electrokinetic phenomena ... 

The value for inferred from the various electrokinetic phenomena is not without ambiguity. The reason lies in the assumptions involved in relating to the measured quantity. Here we will pay attention to some major complications surface conduction, the viscoelectric effect, and the presence of a permeable charged surface coating. 

At the end of the 19 century, the apparent viscosity of some pure insulating liquids vyras found to increase with the application of an electric field [9]. At that time this phenomenon was named the viscoelectric effect. Comprehensive investigations on the electroviscous effect were carried out by Andrade [10-13], According to Andrade and Dodd, there is no measurable effect found in non-polar liquids, but with polar liquids there is a small effect that can be expressed as ... 

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