The effect of packing density of cellulose plugs on streaming potential phenomena

An experimental investigation on streaming potentials of porous plugs of cellulose in both the linear and the non-linear range is described. The variation of the electrokinetic coefficients as a function of fibre concentration in the porous pad has been studied, using solutions of different concentration of Congo Red dye as a permeant. The trend observed for changes of both linear electrokinetic coefficientL ₂₁ and non-linear coefficientL ₂₁₁ as packing density,c _F, increases, is somewhat analogous, the similarity suggesting some proportionality between both coefficients. The electroviscous effect accounts for the decrease ofL ₂₁₁ with the increase ofc _F. The coefficientL ₂₂₁ was found to be always negative and, in absolute value, to decrease with increasingc _F. Second-order coefficients have been interpreted in terms of modifications of “generalized conductivities” produced by the changes of thermodynamic forces.