ELECTROKINETIC PROPERTIES OF CELLULOSE FIBERS: II. ZETA-POTENTIAL MEASUREMENTS BY THE STREAM-COMPRESSION METHOD

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Abstract
A new technique of measuring the ζ-potential of cellulose fibers, in which stream current potential measurements are carried out over a range of solid concentrations on a single pad, is described. In employing the stream potential method it is necessary to measure the d-c. resistance of the pad, since a pronounced dispersion effect yields a-c. resistance values which are in considerable error. Reversible electrodes must therefore be used and since stream current measurements can then be carried out, this simpler method is preferred. Degrees of swelling calculated from the stream data are consistently higher than those calculated from permeability measurements. This discrepancy indicates a serious limitation of the conventional electrokinetic theory when applied to swollen cellulose. A model of the fiber–liquid interface, consisting of partially dissolved electrically charged cellulose chains accounting for the observed discrepancy, is discussed. If this model is applicable, the physical significance of the ζ-potential becomes extremely complex.

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