It was found that the sign of the suspension effect is closely related with the electric charge of the solid particles. For laterite, red loam and coagulated albumin, there appeared an acid suspension effect at higher pH and alkaline effect at lower pH, with a zero ΔpH between the suspension and the supernatent solution at their isoelectric points. When either the glass electrode or the calomel electrode is transferred from the solution to the suspension or vice versa, suspension effect will result. The relative magnitude contributed by the two electrodes depends on the pH value. For the laterite with an iso-electric point of about pH 5.0, the sign of ΔpH due to the glass electrode is always negative and its numerical value increases with pH, whereas the sign of ΔpH due to liquid junction potentials depends on the pH of the suspension, being rather small in magnitude at higher pH. Further observations revealed that factors influencing the liquid iunction potentials are rather complicated indeed.In addition to the sign of the net charge of the particles,many other factors,such as the kind of cations participating in the diffusion process between the two phases as well as the diffusion conditions,may all influence the diffusion potential to some extent.The volume charge density of the sediment also affects the magnitude of the liquid iunction potential.For negatively charged clays,exchangeable hydrogen or sodium ions caused a norfnal negative △pH,calcium ions rendered the liquid junction potential to drop,and at lower pH the sign of △pH caused by trivalent aluminum ions may be reversed from what had been suspected.Stirring of the system affects the pH reading markedly.This effect is confined exclusively to the liquid iunction Potential.