Suspensions/Dispersions are encountered in a wide range of applications, e.g., liquid abrasive cleaners, ceramics, medicines, inks, paints?.etc. In most cases it is necessary to keep the suspension stable for the product lifetime. A new modified differential sedimentation measuring system is suggested and used to identify physical parameters affecting the sedimentation in suspensions. The technique is discussed in details. It is found that particle sizes as well as viscosity of continuous phase are the most important factors governing the stability of a suspension. Empirical relations are extracted to quantitatively describe the weight effect of each factor. The modified measuring system shows good accuracy enough to detect fluctuations in concentration of suspended particles due to their Brownian diffusion, as well as the particles concentrations in the stable suspension. This study confirmed the fact that particles diameters measured by Zetasizer are much greater than those measured by the transmission electron microscope. This study presents a proposal for new technique for particle size separation based on the differential sedimentation in viscose fluids. This new method is a differential viscosity column. The proposed size separation technique may help to separate engineered nano-particles with higher resolution.