Electrical properties of wood Determination of ionic transference numbers and electroosmotic water flow in PinussylvestrisL. (Scots pine)

Abstract

A novel technique has been developed for measuring the electrical transport of ions and of water through natural materials when a dc electric field is applied across them. The material studied was green sapwood of Pinussylvestris L. (Scots pine). By means of a special cell the processes at the wood/solution interfaces were separated from those at the solution/electrode interfaces. Analyses of the electrode compartment solutions after the passage of known numbers of coulombs yielded the relative transference numbers of ions in the wood. Horizontal capillaries in the two electrode compartments enabled equal hydrostatic pressure to be maintained across the cell and allowed the simultaneous measurement of the electroosmotic water flow. This provided a value for the zeta potential of the green sapwood.

The experiments showed electroosmotic water flow and ionic migration to be independent processes. The endogenous inorganic current carriers in the samples decreased in the sequence K⁺, Ca²⁺>Mg²⁺>Na⁺>NH₄⁺, Cl^-, SO₄^2- and values were obtained for the hindered conductances of the major ionic carriers. The results are consistent with a cation-exchange model for the wood.

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