土壤电荷对盐桥的液接电位的长距离影响

Jenny^3]等和Coleman等^2]发现,当将参比电极的盐桥插入土壤悬液中时,带电荷的土壤颗粒可以使盐桥中阳离子和阴离子的淌度发生改变,因而在与土壤溶液的接触界面产生一个液接(扩散)电位.这个液接电位受一系列因素的影响.^1]一般认为,这个液接电位与土壤胶体双电层的存在有关.在胶体化学上.普遍的概念是双电层的(有效)厚度为数百至数千埃.

LONG-RANGE EFFECT OF CHARGED SOIL CLAY ON LIQUID-JUNCTION POTENTIAL OF SALT BRIDGE

It is well-known that the charged soil clay induces a liquid-junction(diffusion) potential at the interface salt bridge-clay sediment.However,careful observations revealed that it was not necessary for the soil to directly contact the salt bridge to create such an effect.Soil mass could cause a liquid-junction potential with a thickness of several millimeters from the surface outwards,and the sign and the magnitude of the potential were closely related to.the charge of the soil.The yellow brown soil carrying a net negative charge caused a negative potential,while the potential caused by latosol carrying net positive charge wa,positive in sign.When the soil clay was mixed with silica powder to decrease the volume charge density of the soil mass,the potential decreased.This long-range effect on the liquid-junetion potential is directly in conflict with the commonly accepted concept about the electrical double layer,in which the effective thickness of the layer is visualized to be only several thousand Angstrom units.