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.